diff --git a/example/CMakeLists.txt b/example/CMakeLists.txt
index dae84e825d..ac1f6ae895 100644
--- a/example/CMakeLists.txt
+++ b/example/CMakeLists.txt
@@ -31,6 +31,10 @@ target_include_directories(example_utils INTERFACE include)
 function(add_example target)
     add_executable(${target} ${target}.cpp)
     target_link_libraries(${target} PRIVATE ${ARGN})
+    if(TARGET mp-units::modules)
+        target_link_libraries(${target} PRIVATE mp-units::modules)
+        target_compile_definitions(${target} PRIVATE MP_UNITS_MODULES)
+    endif()
 endfunction()
 
 add_example(avg_speed mp-units::core-io mp-units::si mp-units::cgs mp-units::usc)
diff --git a/example/avg_speed.cpp b/example/avg_speed.cpp
index 3c2ce2dc75..ba8e968bc6 100644
--- a/example/avg_speed.cpp
+++ b/example/avg_speed.cpp
@@ -20,13 +20,17 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <exception>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/ostream.h>
 #include <mp-units/systems/cgs/cgs.h>
 #include <mp-units/systems/international/international.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
-#include <exception>
-#include <iostream>
+#endif
 
 namespace {
 
diff --git a/example/capacitor_time_curve.cpp b/example/capacitor_time_curve.cpp
index d1fb12ce18..02bbc2719f 100644
--- a/example/capacitor_time_curve.cpp
+++ b/example/capacitor_time_curve.cpp
@@ -20,11 +20,15 @@
     physical_quantities
 */
 
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/math.h>  // IWYU pragma: keep
 #include <mp-units/ostream.h>
 #include <mp-units/systems/isq/electromagnetism.h>
 #include <mp-units/systems/si/si.h>
-#include <iostream>
+#endif
 
 int main()
 {
diff --git a/example/clcpp_response.cpp b/example/clcpp_response.cpp
index fb9f93e3ab..58cdd912ef 100644
--- a/example/clcpp_response.cpp
+++ b/example/clcpp_response.cpp
@@ -15,6 +15,11 @@
  along with this program. If not, see http://www.gnu.org/licenses./
 */
 
+#include <mp-units/bits/fmt_hacks.h>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/ostream.h>
 #include <mp-units/systems/iau/iau.h>
@@ -24,7 +29,7 @@
 #include <mp-units/systems/si/si.h>
 #include <mp-units/systems/typographic/typographic.h>
 #include <mp-units/systems/usc/usc.h>
-#include <iostream>
+#endif
 
 namespace {
 
diff --git a/example/conversion_factor.cpp b/example/conversion_factor.cpp
index a3b810512e..f75d4bf7b6 100644
--- a/example/conversion_factor.cpp
+++ b/example/conversion_factor.cpp
@@ -15,12 +15,17 @@
  along with this program. If not, see http://www.gnu.org/licenses./
 */
 
+#include <mp-units/bits/fmt_hacks.h>
+#include <iostream>
+#include <type_traits>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
 #include <mp-units/systems/si/units.h>
-#include <iostream>
-#include <type_traits>
+#endif
 
 /*
   get conversion factor from one dimensionally equivalent
diff --git a/example/currency.cpp b/example/currency.cpp
index 587f1f7dac..aa1d11acfe 100644
--- a/example/currency.cpp
+++ b/example/currency.cpp
@@ -20,11 +20,16 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <mp-units/quantity_spec_macro.h>
+#include <iostream>
+#include <map>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/ostream.h>
 #include <mp-units/quantity.h>
 #include <mp-units/quantity_point.h>
-#include <iostream>
-#include <map>
+#endif
 
 using namespace mp_units;
 
diff --git a/example/foot_pound_second.cpp b/example/foot_pound_second.cpp
index 092f0d236a..be88f3b432 100644
--- a/example/foot_pound_second.cpp
+++ b/example/foot_pound_second.cpp
@@ -20,14 +20,19 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <mp-units/bits/fmt_hacks.h>
+#include <iostream>
+#include <string_view>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/systems/imperial/imperial.h>
 #include <mp-units/systems/international/international.h>
 #include <mp-units/systems/isq/mechanics.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
-#include <iostream>
-#include <string_view>
+#endif
 
 using namespace mp_units;
 using namespace mp_units::international::unit_symbols;
diff --git a/example/glide_computer_lib/CMakeLists.txt b/example/glide_computer_lib/CMakeLists.txt
index cd6cbcaec7..0a689b11e4 100644
--- a/example/glide_computer_lib/CMakeLists.txt
+++ b/example/glide_computer_lib/CMakeLists.txt
@@ -25,3 +25,7 @@ cmake_minimum_required(VERSION 3.2)
 add_library(glide_computer_lib STATIC glide_computer_lib.cpp include/glide_computer_lib.h)
 target_link_libraries(glide_computer_lib PRIVATE mp-units::core-fmt PUBLIC mp-units::si mp-units::utility example_utils)
 target_include_directories(glide_computer_lib PUBLIC include)
+if(TARGET mp-units::modules)
+    target_link_libraries(glide_computer_lib PRIVATE mp-units::modules)
+    target_compile_definitions(glide_computer_lib PRIVATE MP_UNITS_MODULES)
+endif()
diff --git a/example/glide_computer_lib/glide_computer_lib.cpp b/example/glide_computer_lib/glide_computer_lib.cpp
index c0fa44d7bf..46d2c9ce89 100644
--- a/example/glide_computer_lib/glide_computer_lib.cpp
+++ b/example/glide_computer_lib/glide_computer_lib.cpp
@@ -21,10 +21,14 @@
 // SOFTWARE.
 
 #include "glide_computer_lib.h"
-#include <mp-units/format.h>
 #include <iostream>
 #include <numeric>
 #include <string_view>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
+#include <mp-units/format.h>
+#endif
 
 namespace glide_computer {
 
diff --git a/example/glide_computer_lib/include/glide_computer_lib.h b/example/glide_computer_lib/include/glide_computer_lib.h
index 8503cc3b0c..9adfae1821 100644
--- a/example/glide_computer_lib/include/glide_computer_lib.h
+++ b/example/glide_computer_lib/include/glide_computer_lib.h
@@ -22,11 +22,9 @@
 
 #pragma once
 
+#include <mp-units/quantity_spec_macro.h>
+//
 #include "geographic.h"
-#include <mp-units/chrono.h>
-#include <mp-units/math.h>  // IWYU pragma: keep
-#include <mp-units/quantity_point.h>
-#include <mp-units/systems/isq/space_and_time.h>
 #include <algorithm>
 #include <array>
 #include <initializer_list>
@@ -35,6 +33,14 @@
 #include <ranges>
 #include <string>  // IWYU pragma: keep
 #include <vector>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
+#include <mp-units/chrono.h>
+#include <mp-units/math.h>  // IWYU pragma: keep
+#include <mp-units/quantity_point.h>
+#include <mp-units/systems/isq/space_and_time.h>
+#endif
 
 // An example of a really simplified tactical glide computer
 // Simplifications:
diff --git a/example/hello_units.cpp b/example/hello_units.cpp
index 041bbf8488..2a6e8700c2 100644
--- a/example/hello_units.cpp
+++ b/example/hello_units.cpp
@@ -25,12 +25,17 @@
 // !!! renders correctly in the documentation "Examples" section.                 !!!
 // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
+#include <mp-units/bits/fmt_hacks.h>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/ostream.h>
 #include <mp-units/systems/international/international.h>
 #include <mp-units/systems/isq/isq.h>
 #include <mp-units/systems/si/si.h>
-#include <iostream>
+#endif
 
 using namespace mp_units;
 
diff --git a/example/include/geographic.h b/example/include/geographic.h
index 574b086566..08148d50fd 100644
--- a/example/include/geographic.h
+++ b/example/include/geographic.h
@@ -24,16 +24,20 @@
 
 #include "ranged_representation.h"
 #include <mp-units/bits/fmt_hacks.h>
+#include <compare>
+#include <limits>
+#include <numbers>
+#include <ostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/math.h>
 #include <mp-units/quantity.h>
 #include <mp-units/quantity_point.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/units.h>
-#include <compare>
-#include <limits>
-#include <numbers>
-#include <ostream>
+#endif
 
 namespace geographic {
 
diff --git a/example/include/ranged_representation.h b/example/include/ranged_representation.h
index 60bab6fe91..aaeaca0a85 100644
--- a/example/include/ranged_representation.h
+++ b/example/include/ranged_representation.h
@@ -24,10 +24,14 @@
 
 #include "validated_type.h"
 #include <mp-units/bits/external/hacks.h>
-#include <mp-units/customization_points.h>
 #include <algorithm>
 #include <concepts>
 #include <type_traits>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
+#include <mp-units/customization_points.h>
+#endif
 
 template<std::movable T, MP_UNITS_CONSTRAINED_NTTP_WORKAROUND(std::convertible_to<T>) auto Min,
          MP_UNITS_CONSTRAINED_NTTP_WORKAROUND(std::convertible_to<T>) auto Max>
diff --git a/example/kalman_filter/CMakeLists.txt b/example/kalman_filter/CMakeLists.txt
index f137001899..8be30a0afd 100644
--- a/example/kalman_filter/CMakeLists.txt
+++ b/example/kalman_filter/CMakeLists.txt
@@ -28,6 +28,10 @@ cmake_minimum_required(VERSION 3.2)
 function(add_example target)
     add_executable(${target} ${target}.cpp)
     target_link_libraries(${target} PRIVATE ${ARGN})
+    if(TARGET mp-units::modules)
+        target_link_libraries(${target} PRIVATE mp-units::modules)
+        target_compile_definitions(${target} PRIVATE MP_UNITS_MODULES)
+    endif()
 endfunction()
 
 add_example(kalman_filter-example_1 mp-units::core-fmt mp-units::si mp-units::utility)
diff --git a/example/kalman_filter/kalman.h b/example/kalman_filter/kalman.h
index 0d38ebaa78..de888bcd2a 100644
--- a/example/kalman_filter/kalman.h
+++ b/example/kalman_filter/kalman.h
@@ -23,12 +23,16 @@
 #pragma once
 
 #include <mp-units/bits/fmt_hacks.h>
+#include <tuple>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/math.h>
 #include <mp-units/quantity.h>
 #include <mp-units/quantity_point.h>
 #include <mp-units/systems/isq/space_and_time.h>
-#include <tuple>
+#endif
 
 namespace kalman {
 
diff --git a/example/kalman_filter/kalman_filter-example_1.cpp b/example/kalman_filter/kalman_filter-example_1.cpp
index bee7176107..c038f253eb 100644
--- a/example/kalman_filter/kalman_filter-example_1.cpp
+++ b/example/kalman_filter/kalman_filter-example_1.cpp
@@ -21,11 +21,15 @@
 // SOFTWARE.
 
 #include "kalman.h"
+#include <array>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
-#include <array>
-#include <iostream>
+#endif
 
 // Based on: https://www.kalmanfilter.net/alphabeta.html#ex1
 
diff --git a/example/kalman_filter/kalman_filter-example_2.cpp b/example/kalman_filter/kalman_filter-example_2.cpp
index b7b4171462..076492af35 100644
--- a/example/kalman_filter/kalman_filter-example_2.cpp
+++ b/example/kalman_filter/kalman_filter-example_2.cpp
@@ -21,11 +21,15 @@
 // SOFTWARE.
 
 #include "kalman.h"
+#include <array>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
-#include <array>
-#include <iostream>
+#endif
 
 // Based on: https://www.kalmanfilter.net/alphabeta.html#ex2
 
diff --git a/example/kalman_filter/kalman_filter-example_3.cpp b/example/kalman_filter/kalman_filter-example_3.cpp
index 30e11f4354..6aa59dca21 100644
--- a/example/kalman_filter/kalman_filter-example_3.cpp
+++ b/example/kalman_filter/kalman_filter-example_3.cpp
@@ -21,11 +21,15 @@
 // SOFTWARE.
 
 #include "kalman.h"
+#include <array>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
-#include <array>
-#include <iostream>
+#endif
 
 // Based on: https://www.kalmanfilter.net/alphabeta.html#ex3
 
diff --git a/example/kalman_filter/kalman_filter-example_4.cpp b/example/kalman_filter/kalman_filter-example_4.cpp
index f0c4a2b26f..6036420028 100644
--- a/example/kalman_filter/kalman_filter-example_4.cpp
+++ b/example/kalman_filter/kalman_filter-example_4.cpp
@@ -21,11 +21,15 @@
 // SOFTWARE.
 
 #include "kalman.h"
+#include <array>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
-#include <array>
-#include <iostream>
+#endif
 
 // Based on: https://www.kalmanfilter.net/alphabeta.html#ex4
 
diff --git a/example/kalman_filter/kalman_filter-example_5.cpp b/example/kalman_filter/kalman_filter-example_5.cpp
index e50114ebcf..b4be7e3c1e 100644
--- a/example/kalman_filter/kalman_filter-example_5.cpp
+++ b/example/kalman_filter/kalman_filter-example_5.cpp
@@ -21,12 +21,16 @@
 // SOFTWARE.
 
 #include "kalman.h"
+#include <array>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/math.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
-#include <array>
-#include <iostream>
+#endif
 
 // Based on: https://www.kalmanfilter.net/kalman1d.html#ex5
 
diff --git a/example/kalman_filter/kalman_filter-example_6.cpp b/example/kalman_filter/kalman_filter-example_6.cpp
index ec2954088f..ad00787ada 100644
--- a/example/kalman_filter/kalman_filter-example_6.cpp
+++ b/example/kalman_filter/kalman_filter-example_6.cpp
@@ -21,13 +21,17 @@
 // SOFTWARE.
 
 #include "kalman.h"
+#include <array>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/math.h>
 #include <mp-units/quantity_point.h>
 #include <mp-units/systems/isq/thermodynamics.h>
 #include <mp-units/systems/si/si.h>
-#include <array>
-#include <iostream>
+#endif
 
 // Based on: https://www.kalmanfilter.net/kalman1d.html#ex6
 
diff --git a/example/kalman_filter/kalman_filter-example_7.cpp b/example/kalman_filter/kalman_filter-example_7.cpp
index 613a6da7cc..aecf79857d 100644
--- a/example/kalman_filter/kalman_filter-example_7.cpp
+++ b/example/kalman_filter/kalman_filter-example_7.cpp
@@ -21,13 +21,17 @@
 // SOFTWARE.
 
 #include "kalman.h"
+#include <array>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/math.h>
 #include <mp-units/quantity_point.h>
 #include <mp-units/systems/isq/thermodynamics.h>
 #include <mp-units/systems/si/si.h>
-#include <array>
-#include <iostream>
+#endif
 
 // Based on: https://www.kalmanfilter.net/kalman1d.html#ex7
 
diff --git a/example/kalman_filter/kalman_filter-example_8.cpp b/example/kalman_filter/kalman_filter-example_8.cpp
index 081b8507b8..a5ecbdff36 100644
--- a/example/kalman_filter/kalman_filter-example_8.cpp
+++ b/example/kalman_filter/kalman_filter-example_8.cpp
@@ -21,13 +21,17 @@
 // SOFTWARE.
 
 #include "kalman.h"
+#include <array>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/math.h>
 #include <mp-units/quantity_point.h>
 #include <mp-units/systems/isq/thermodynamics.h>
 #include <mp-units/systems/si/si.h>
-#include <array>
-#include <iostream>
+#endif
 
 // Based on: https://www.kalmanfilter.net/kalman1d.html#ex8
 
diff --git a/example/measurement.cpp b/example/measurement.cpp
index b11492af0d..89f693c6f4 100644
--- a/example/measurement.cpp
+++ b/example/measurement.cpp
@@ -20,13 +20,17 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <cmath>
+#include <exception>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/ostream.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
 #include <mp-units/systems/si/units.h>
-#include <cmath>
-#include <exception>
-#include <iostream>
+#endif
 
 namespace {
 
diff --git a/example/si_constants.cpp b/example/si_constants.cpp
index 99355a611a..26ebf2d82d 100644
--- a/example/si_constants.cpp
+++ b/example/si_constants.cpp
@@ -25,9 +25,14 @@
 // !!! renders correctly in the documentation "Examples" section.                 !!!
 // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
+#include <mp-units/bits/fmt_hacks.h>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/systems/si/si.h>
-#include <iostream>
+#endif
 
 template<class T>
   requires mp_units::is_scalar<T>
diff --git a/example/spectroscopy_units.cpp b/example/spectroscopy_units.cpp
index 6cf9e953fd..6a4673e5a3 100644
--- a/example/spectroscopy_units.cpp
+++ b/example/spectroscopy_units.cpp
@@ -20,11 +20,16 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <mp-units/bits/fmt_hacks.h>
+#include <iostream>
+#include <tuple>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/systems/isq/isq.h>
 #include <mp-units/systems/si/si.h>
-#include <iostream>
-#include <tuple>
+#endif
 
 // This example implements a table of units provided in the following article
 // http://cds.cern.ch/record/1481609/files/978-3-642-18018-7_BookBackMatter.pdf
diff --git a/example/storage_tank.cpp b/example/storage_tank.cpp
index 4ec3f725f3..8719320b92 100644
--- a/example/storage_tank.cpp
+++ b/example/storage_tank.cpp
@@ -20,6 +20,15 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <mp-units/bits/fmt_hacks.h>
+#include <mp-units/quantity_spec_macro.h>
+#include <cassert>
+#include <iostream>
+#include <numbers>
+#include <utility>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/math.h>
 #include <mp-units/systems/isq/mechanics.h>
@@ -27,10 +36,7 @@
 #include <mp-units/systems/si/constants.h>
 #include <mp-units/systems/si/unit_symbols.h>
 #include <mp-units/systems/si/units.h>
-#include <cassert>
-#include <iostream>
-#include <numbers>
-#include <utility>
+#endif
 
 template<class T>
   requires mp_units::is_scalar<T>
diff --git a/example/strong_angular_quantities.cpp b/example/strong_angular_quantities.cpp
index 7d375e3cd2..298a097e78 100644
--- a/example/strong_angular_quantities.cpp
+++ b/example/strong_angular_quantities.cpp
@@ -20,11 +20,15 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/math.h>
 #include <mp-units/ostream.h>
 #include <mp-units/systems/isq_angle/isq_angle.h>
 #include <mp-units/systems/si/unit_symbols.h>
-#include <iostream>
+#endif
 
 template<class T>
   requires mp_units::is_scalar<T>
diff --git a/example/total_energy.cpp b/example/total_energy.cpp
index 9d6a9f8b6d..86d4217e14 100644
--- a/example/total_energy.cpp
+++ b/example/total_energy.cpp
@@ -20,14 +20,18 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <exception>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/math.h>
 #include <mp-units/ostream.h>
 #include <mp-units/systems/isq/mechanics.h>
 #include <mp-units/systems/natural/natural.h>
 #include <mp-units/systems/si/constants.h>
 #include <mp-units/systems/si/unit_symbols.h>
-#include <exception>
-#include <iostream>
+#endif
 
 template<class T>
   requires mp_units::is_scalar<T>
diff --git a/example/unmanned_aerial_vehicle.cpp b/example/unmanned_aerial_vehicle.cpp
index 56ecd8285c..ef1a8b1c40 100644
--- a/example/unmanned_aerial_vehicle.cpp
+++ b/example/unmanned_aerial_vehicle.cpp
@@ -21,13 +21,18 @@
 // SOFTWARE.
 
 #include "geographic.h"
+#include <mp-units/bits/fmt_hacks.h>
+#include <cassert>
+#include <iostream>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/ostream.h>
 #include <mp-units/quantity_point.h>
 #include <mp-units/systems/international/international.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
-#include <cassert>
-#include <iostream>
+#endif
 
 using namespace mp_units;
 using namespace geographic;
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index c0249ea936..fe1653a888 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -51,6 +51,20 @@ target_link_libraries(
 add_library(mp-units::mp-units ALIAS mp-units)
 install(TARGETS mp-units EXPORT mp-unitsTargets)
 
+# C++ module
+if(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API)
+    add_library(mp-units-modules STATIC)
+    add_library(mp-units::modules ALIAS mp-units-modules)
+    target_sources(
+        mp-units-modules PUBLIC FILE_SET CXX_MODULES BASE_DIRS "${CMAKE_CURRENT_SOURCE_DIR}" FILES "mp-units.cpp"
+    )
+    target_link_libraries(mp-units-modules PRIVATE mp-units::mp-units)
+    target_include_directories(
+        mp-units-modules ${unitsAsSystem} INTERFACE $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/core/include>
+                                                    $<INSTALL_INTERFACE:include>
+    )
+endif()
+
 # local build
 export(EXPORT mp-unitsTargets NAMESPACE mp-units::)
 configure_file("mp-unitsConfig.cmake" "." COPYONLY)
diff --git a/src/core/include/mp-units/bits/external/type_list.h b/src/core/include/mp-units/bits/external/type_list.h
index 5369ce18db..80b66e060f 100644
--- a/src/core/include/mp-units/bits/external/type_list.h
+++ b/src/core/include/mp-units/bits/external/type_list.h
@@ -24,6 +24,7 @@
 
 #include <mp-units/bits/external/hacks.h>  // IWYU pragma: keep
 #include <cstddef>
+#include <type_traits>
 #include <utility>
 
 MP_UNITS_DIAGNOSTIC_PUSH
diff --git a/src/core/include/mp-units/quantity_spec.h b/src/core/include/mp-units/quantity_spec.h
index 0bd2fe95e3..805182f971 100644
--- a/src/core/include/mp-units/quantity_spec.h
+++ b/src/core/include/mp-units/quantity_spec.h
@@ -32,6 +32,7 @@
 #include <mp-units/bits/reference_concepts.h>
 #include <mp-units/bits/representation_concepts.h>
 #include <mp-units/dimension.h>
+#include <mp-units/quantity_spec_macro.h>
 #include <tuple>
 
 namespace mp_units {
@@ -359,20 +360,6 @@ struct quantity_spec<Self, QS, Eq, Args...> : quantity_spec<Self, QS, Args...> {
   static constexpr quantity_character character = detail::quantity_character_init<Args...>(Eq.character);
 };
 
-#ifdef __cpp_explicit_this_parameter
-
-#define QUANTITY_SPEC(name, ...)                                          \
-  inline constexpr struct name : ::mp_units::quantity_spec<__VA_ARGS__> { \
-  } name
-
-#else
-
-#define QUANTITY_SPEC(name, ...)                                                \
-  inline constexpr struct name : ::mp_units::quantity_spec<name, __VA_ARGS__> { \
-  } name
-
-#endif
-
 
 /**
  * @brief A specification of a derived quantity
diff --git a/src/core/include/mp-units/quantity_spec_macro.h b/src/core/include/mp-units/quantity_spec_macro.h
new file mode 100644
index 0000000000..9e45b833df
--- /dev/null
+++ b/src/core/include/mp-units/quantity_spec_macro.h
@@ -0,0 +1,37 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#pragma once
+
+#ifdef __cpp_explicit_this_parameter
+
+#define QUANTITY_SPEC(name, ...)                                          \
+  inline constexpr struct name : ::mp_units::quantity_spec<__VA_ARGS__> { \
+  } name
+
+#else
+
+#define QUANTITY_SPEC(name, ...)                                                \
+  inline constexpr struct name : ::mp_units::quantity_spec<name, __VA_ARGS__> { \
+  } name
+
+#endif
diff --git a/src/mp-units.cpp b/src/mp-units.cpp
new file mode 100644
index 0000000000..aff96a3988
--- /dev/null
+++ b/src/mp-units.cpp
@@ -0,0 +1,67 @@
+module;
+
+// core
+#include <gsl/gsl-lite.hpp>
+#include <array>
+#include <compare>
+#include <concepts>
+#include <cstddef>
+#include <cstdint>
+#include <functional>
+#include <initializer_list>
+#include <iterator>
+#include <limits>
+#include <numbers>
+#include <numeric>
+#include <optional>
+#include <ranges>
+#include <string>
+#include <string_view>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+// core-io
+#include <sstream>
+
+// core-fmt
+#include <mp-units/bits/fmt_hacks.h>
+
+// utility
+#include <chrono>
+#include <cmath>
+#include <random>
+
+export module mp_units;
+
+export
+{
+// core
+#include <mp-units/core.h>
+
+// core-io
+#include <mp-units/ostream.h>
+
+// core-fmt
+#include <mp-units/format.h>
+
+// systems
+#include <mp-units/systems/angular/angular.h>
+#include <mp-units/systems/cgs/cgs.h>
+#include <mp-units/systems/hep/hep.h>
+#include <mp-units/systems/iau/iau.h>
+#include <mp-units/systems/iec80000/iec80000.h>
+#include <mp-units/systems/imperial/imperial.h>
+#include <mp-units/systems/international/international.h>
+#include <mp-units/systems/isq/isq.h>
+#include <mp-units/systems/isq_angle/isq_angle.h>
+#include <mp-units/systems/natural/natural.h>
+#include <mp-units/systems/si/si.h>
+#include <mp-units/systems/typographic/typographic.h>
+#include <mp-units/systems/usc/usc.h>
+
+// utility
+#include <mp-units/chrono.h>
+#include <mp-units/math.h>
+#include <mp-units/random.h>
+}
diff --git a/src/utility/include/mp-units/random.h b/src/utility/include/mp-units/random.h
index 2c26b97a97..811494875d 100644
--- a/src/utility/include/mp-units/random.h
+++ b/src/utility/include/mp-units/random.h
@@ -30,7 +30,7 @@ namespace mp_units {
 
 namespace detail {
 template<Quantity Q, typename InputIt>
-static std::vector<typename Q::rep> i_qty_to_rep(InputIt first, InputIt last)
+std::vector<typename Q::rep> i_qty_to_rep(InputIt first, InputIt last)
 {
   std::vector<typename Q::rep> intervals_rep;
   intervals_rep.reserve(static_cast<size_t>(std::distance(first, last)));
@@ -41,7 +41,7 @@ static std::vector<typename Q::rep> i_qty_to_rep(InputIt first, InputIt last)
 }
 
 template<Quantity Q>
-static std::vector<typename Q::rep> bl_qty_to_rep(std::initializer_list<Q>& bl)
+std::vector<typename Q::rep> bl_qty_to_rep(std::initializer_list<Q>& bl)
 {
   std::vector<typename Q::rep> bl_rep;
   bl_rep.reserve(bl.size());
@@ -52,7 +52,7 @@ static std::vector<typename Q::rep> bl_qty_to_rep(std::initializer_list<Q>& bl)
 }
 
 template<Quantity Q, typename UnaryOperation>
-inline static std::vector<typename Q::rep> fw_bl_pwc(std::initializer_list<Q>& bl, UnaryOperation fw)
+std::vector<typename Q::rep> fw_bl_pwc(std::initializer_list<Q>& bl, UnaryOperation fw)
 {
   using rep = MP_UNITS_TYPENAME Q::rep;
   std::vector<rep> w_bl;
@@ -70,7 +70,7 @@ inline static std::vector<typename Q::rep> fw_bl_pwc(std::initializer_list<Q>& b
 }
 
 template<Quantity Q, typename UnaryOperation>
-static std::vector<typename Q::rep> fw_bl_pwl(std::initializer_list<Q>& bl, UnaryOperation fw)
+std::vector<typename Q::rep> fw_bl_pwl(std::initializer_list<Q>& bl, UnaryOperation fw)
 {
   std::vector<typename Q::rep> weights;
   weights.reserve(bl.size());
diff --git a/test/unit_test/runtime/almost_equals.h b/test/unit_test/runtime/almost_equals.h
index 69b972c1ec..adff079d91 100644
--- a/test/unit_test/runtime/almost_equals.h
+++ b/test/unit_test/runtime/almost_equals.h
@@ -21,8 +21,12 @@
 // SOFTWARE.
 
 #include <catch2/matchers/catch_matchers_templated.hpp>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/format.h>
 #include <mp-units/quantity.h>
+#endif
 
 namespace mp_units {
 
diff --git a/test/unit_test/runtime/distribution_test.cpp b/test/unit_test/runtime/distribution_test.cpp
index b7f459713e..c33654289a 100644
--- a/test/unit_test/runtime/distribution_test.cpp
+++ b/test/unit_test/runtime/distribution_test.cpp
@@ -21,14 +21,18 @@
 // SOFTWARE.
 
 #include <catch2/catch_test_macros.hpp>
-#include <mp-units/ostream.h>
-#include <mp-units/random.h>
-#include <mp-units/systems/si/unit_symbols.h>
-#include <mp-units/systems/si/units.h>
 #include <array>
 #include <initializer_list>
 #include <random>
 #include <vector>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
+#include <mp-units/ostream.h>
+#include <mp-units/random.h>
+#include <mp-units/systems/si/unit_symbols.h>
+#include <mp-units/systems/si/units.h>
+#endif
 
 
 using namespace mp_units;
diff --git a/test/unit_test/runtime/fmt_test.cpp b/test/unit_test/runtime/fmt_test.cpp
index 9bdce188b4..8edefbac08 100644
--- a/test/unit_test/runtime/fmt_test.cpp
+++ b/test/unit_test/runtime/fmt_test.cpp
@@ -22,6 +22,12 @@
 
 #include <catch2/catch_test_macros.hpp>
 #include <catch2/matchers/catch_matchers_exception.hpp>
+#include <iomanip>
+#include <limits>
+#include <locale>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/customization_points.h>
 #include <mp-units/format.h>
 #include <mp-units/ostream.h>
@@ -29,9 +35,7 @@
 #include <mp-units/systems/isq/mechanics.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/si.h>
-#include <iomanip>
-#include <limits>
-#include <locale>
+#endif
 
 template<class T>
   requires mp_units::is_scalar<T>
diff --git a/test/unit_test/runtime/math_test.cpp b/test/unit_test/runtime/math_test.cpp
index 4e838273ea..e513deec31 100644
--- a/test/unit_test/runtime/math_test.cpp
+++ b/test/unit_test/runtime/math_test.cpp
@@ -22,13 +22,17 @@
 
 #include "almost_equals.h"
 #include <catch2/catch_all.hpp>
+#include <limits>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/math.h>
 #include <mp-units/ostream.h>
 #include <mp-units/systems/angular/angular.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
 #include <mp-units/systems/si/units.h>
-#include <limits>
+#endif
 
 using namespace mp_units;
 using namespace mp_units::si::unit_symbols;
diff --git a/test/unit_test/static/CMakeLists.txt b/test/unit_test/static/CMakeLists.txt
index d8a6cb04ff..54217b55f4 100644
--- a/test/unit_test/static/CMakeLists.txt
+++ b/test/unit_test/static/CMakeLists.txt
@@ -23,10 +23,16 @@
 cmake_minimum_required(VERSION 3.2)
 
 add_library(unit_tests_static_truncating quantity_test.cpp)
-target_link_libraries(unit_tests_static_truncating PRIVATE mp-units::mp-units)
-target_compile_options(
-    unit_tests_static_truncating PRIVATE $<IF:$<CXX_COMPILER_ID:MSVC>,/wd4242 /wd4244,-Wno-conversion>
-)
+
+set(no_truncation_warning_targets unit_tests_static_truncating)
+if(TARGET mp-units::modules)
+    list(APPEND no_truncation_warning_targets mp-units-modules)
+    set(mp_units_modules_target mp-units::modules)
+    set(mp_units_modules_macro MP_UNITS_MODULES)
+endif()
+foreach(target IN LISTS no_truncation_warning_targets)
+    target_compile_options("${target}" PRIVATE $<IF:$<CXX_COMPILER_ID:MSVC>,/wd4242 /wd4244,-Wno-conversion>)
+endforeach()
 
 add_library(
     unit_tests_static
@@ -63,5 +69,8 @@ add_library(
     usc_test.cpp
 )
 
-target_link_libraries(unit_tests_static PRIVATE mp-units::mp-units)
-target_link_libraries(unit_tests_static PRIVATE unit_tests_static_truncating mp-units::mp-units)
+target_link_libraries(unit_tests_static PRIVATE unit_tests_static_truncating)
+foreach(target unit_tests_static_truncating unit_tests_static)
+    target_link_libraries(${target} PRIVATE mp-units::mp-units ${mp_units_modules_target})
+    target_compile_definitions(${target} PRIVATE ${mp_units_modules_macro})
+endforeach()
diff --git a/test/unit_test/static/angular_test.cpp b/test/unit_test/static/angular_test.cpp
index c3010dfe86..c0c5a23b6b 100644
--- a/test/unit_test/static/angular_test.cpp
+++ b/test/unit_test/static/angular_test.cpp
@@ -20,8 +20,12 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <mp-units/systems/isq_angle/isq_angle.h>
 #include <numbers>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
+#include <mp-units/systems/isq_angle/isq_angle.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/cgs_test.cpp b/test/unit_test/static/cgs_test.cpp
index e0b36fffb2..79d86129a3 100644
--- a/test/unit_test/static/cgs_test.cpp
+++ b/test/unit_test/static/cgs_test.cpp
@@ -21,10 +21,14 @@
 // SOFTWARE.
 
 #include "test_tools.h"
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/systems/cgs/cgs.h>
 #include <mp-units/systems/isq/mechanics.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
+#endif
 
 template<class T>
   requires mp_units::is_scalar<T>
diff --git a/test/unit_test/static/chrono_test.cpp b/test/unit_test/static/chrono_test.cpp
index 75d87128ef..25a69920ef 100644
--- a/test/unit_test/static/chrono_test.cpp
+++ b/test/unit_test/static/chrono_test.cpp
@@ -21,11 +21,16 @@
 // SOFTWARE.
 
 #include "test_tools.h"
+#include <ratio>
+#ifdef MP_UNITS_MODULES
+#include <chrono>
+import mp_units;
+#else
 #include <mp-units/bits/external/type_traits.h>
 #include <mp-units/chrono.h>
 #include <mp-units/quantity_point.h>
 #include <mp-units/systems/si/unit_symbols.h>
-#include <ratio>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/concepts_test.cpp b/test/unit_test/static/concepts_test.cpp
index 21c6cbcc55..e4409295cb 100644
--- a/test/unit_test/static/concepts_test.cpp
+++ b/test/unit_test/static/concepts_test.cpp
@@ -20,16 +20,20 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <chrono>
+#include <complex>
+#include <optional>
+#include <string>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/chrono.h>
 #include <mp-units/concepts.h>
 #include <mp-units/quantity_point.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/natural/natural.h>
 #include <mp-units/systems/si/si.h>
-#include <chrono>
-#include <complex>
-#include <optional>
-#include <string>
+#endif
 
 template<typename T>
 inline constexpr bool mp_units::is_scalar<std::complex<T>> = true;
diff --git a/test/unit_test/static/custom_rep_test_min_expl.cpp b/test/unit_test/static/custom_rep_test_min_expl.cpp
index 689c9666d0..9288679d3e 100644
--- a/test/unit_test/static/custom_rep_test_min_expl.cpp
+++ b/test/unit_test/static/custom_rep_test_min_expl.cpp
@@ -20,11 +20,15 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <ostream>
+#include <type_traits>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <units/generic/dimensionless.h>
 #include <units/isq/si/length.h>
 #include <units/isq/si/prefixes.h>
-#include <ostream>
-#include <type_traits>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/custom_rep_test_min_impl.cpp b/test/unit_test/static/custom_rep_test_min_impl.cpp
index 7d18effd77..2ebc01a695 100644
--- a/test/unit_test/static/custom_rep_test_min_impl.cpp
+++ b/test/unit_test/static/custom_rep_test_min_impl.cpp
@@ -20,8 +20,14 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <mp-units/systems/si/units.h>
+#include <mp-units/bits/external/hacks.h>
+#include <concepts>
 #include <type_traits>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
+#include <mp-units/systems/si/units.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/dimension_test.cpp b/test/unit_test/static/dimension_test.cpp
index d5091f54c9..425b712a2e 100644
--- a/test/unit_test/static/dimension_test.cpp
+++ b/test/unit_test/static/dimension_test.cpp
@@ -21,11 +21,15 @@
 // SOFTWARE.
 
 #include "test_tools.h"
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/dimension.h>
 #include <mp-units/quantity.h>
 #include <mp-units/quantity_spec.h>
 #include <mp-units/reference.h>
 #include <mp-units/unit.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/fixed_string_test.cpp b/test/unit_test/static/fixed_string_test.cpp
index 4835fbdfeb..c4a56aeddc 100644
--- a/test/unit_test/static/fixed_string_test.cpp
+++ b/test/unit_test/static/fixed_string_test.cpp
@@ -20,7 +20,11 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/bits/external/fixed_string.h>
+#endif
 
 using namespace mp_units;
 
diff --git a/test/unit_test/static/fractional_exponent_quantity.cpp b/test/unit_test/static/fractional_exponent_quantity.cpp
index d8a1b51376..6014b34ebb 100644
--- a/test/unit_test/static/fractional_exponent_quantity.cpp
+++ b/test/unit_test/static/fractional_exponent_quantity.cpp
@@ -20,9 +20,14 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <mp-units/quantity_spec_macro.h>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/math.h>
 #include <mp-units/systems/isq/electromagnetism.h>
 #include <mp-units/systems/si/units.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/hep_test.cpp b/test/unit_test/static/hep_test.cpp
index f58e110efe..8be44a11e2 100644
--- a/test/unit_test/static/hep_test.cpp
+++ b/test/unit_test/static/hep_test.cpp
@@ -20,10 +20,14 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/systems/hep/hep.h>
 #include <mp-units/systems/isq/mechanics.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/si.h>
+#endif
 
 template<class T>
   requires mp_units::is_scalar<T>
diff --git a/test/unit_test/static/iau_test.cpp b/test/unit_test/static/iau_test.cpp
index 33ddec6808..7c94c60159 100644
--- a/test/unit_test/static/iau_test.cpp
+++ b/test/unit_test/static/iau_test.cpp
@@ -20,9 +20,13 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/math.h>
 #include <mp-units/systems/iau/iau.h>
 #include <mp-units/systems/si/unit_symbols.h>
+#endif
 
 /* ************** DERIVED DIMENSIONS THAT INCLUDE UNITS WITH SPECIAL NAMES **************** */
 
diff --git a/test/unit_test/static/iec80000_test.cpp b/test/unit_test/static/iec80000_test.cpp
index 4732185385..0780cebe13 100644
--- a/test/unit_test/static/iec80000_test.cpp
+++ b/test/unit_test/static/iec80000_test.cpp
@@ -20,10 +20,14 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/quantity.h>
 #include <mp-units/reference.h>
 #include <mp-units/systems/iec80000/iec80000.h>
 #include <mp-units/systems/si/unit_symbols.h>
+#endif
 
 /* ************** DERIVED DIMENSIONS THAT INCLUDE UNITS WITH SPECIAL NAMES **************** */
 
diff --git a/test/unit_test/static/imperial_test.cpp b/test/unit_test/static/imperial_test.cpp
index 7b3b3a741d..13d1ed2600 100644
--- a/test/unit_test/static/imperial_test.cpp
+++ b/test/unit_test/static/imperial_test.cpp
@@ -20,9 +20,13 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/systems/imperial/imperial.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/international_test.cpp b/test/unit_test/static/international_test.cpp
index a5a312194b..910c9e2605 100644
--- a/test/unit_test/static/international_test.cpp
+++ b/test/unit_test/static/international_test.cpp
@@ -20,12 +20,16 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/math.h>
 #include <mp-units/systems/international/international.h>
 #include <mp-units/systems/isq/mechanics.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/constants.h>
 #include <mp-units/systems/si/units.h>
+#endif
 
 template<class T>
   requires mp_units::is_scalar<T>
diff --git a/test/unit_test/static/isq_angle_test.cpp b/test/unit_test/static/isq_angle_test.cpp
index ef59707664..fdb324963f 100644
--- a/test/unit_test/static/isq_angle_test.cpp
+++ b/test/unit_test/static/isq_angle_test.cpp
@@ -20,8 +20,12 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/systems/isq_angle/isq_angle.h>
 #include <mp-units/systems/si/unit_symbols.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/isq_test.cpp b/test/unit_test/static/isq_test.cpp
index 151e5ad7b5..7f7fe4ed55 100644
--- a/test/unit_test/static/isq_test.cpp
+++ b/test/unit_test/static/isq_test.cpp
@@ -20,9 +20,13 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/reference.h>
 #include <mp-units/systems/isq/isq.h>
 #include <mp-units/systems/si/unit_symbols.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/magnitude_test.cpp b/test/unit_test/static/magnitude_test.cpp
index eaf2cc17c6..f0eb031b8e 100644
--- a/test/unit_test/static/magnitude_test.cpp
+++ b/test/unit_test/static/magnitude_test.cpp
@@ -20,9 +20,13 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <units/bits/magnitude.h>
 #include <units/bits/ratio.h>
 #include <type_traits>
+#endif
 
 using namespace units;
 using namespace units::detail;
diff --git a/test/unit_test/static/math_test.cpp b/test/unit_test/static/math_test.cpp
index a8b23053a0..ed380b5ac4 100644
--- a/test/unit_test/static/math_test.cpp
+++ b/test/unit_test/static/math_test.cpp
@@ -20,11 +20,15 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <optional>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/math.h>  // IWYU pragma: keep
 #include <mp-units/systems/international/international.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
-#include <optional>
+#endif
 
 #if __cpp_lib_constexpr_cmath || MP_UNITS_COMP_GCC
 
diff --git a/test/unit_test/static/natural_test.cpp b/test/unit_test/static/natural_test.cpp
index 5666991fac..5dbc32b50b 100644
--- a/test/unit_test/static/natural_test.cpp
+++ b/test/unit_test/static/natural_test.cpp
@@ -20,8 +20,12 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/math.h>
 #include <mp-units/systems/natural/natural.h>
+#endif
 
 template<class T>
   requires mp_units::is_scalar<T>
diff --git a/test/unit_test/static/prime_test.cpp b/test/unit_test/static/prime_test.cpp
index c75f04afd0..ebbb7d515b 100644
--- a/test/unit_test/static/prime_test.cpp
+++ b/test/unit_test/static/prime_test.cpp
@@ -20,9 +20,13 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#include <mp-units/bits/prime.h>
 #include <type_traits>
 #include <utility>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
+#include <mp-units/bits/prime.h>
+#endif
 
 using namespace mp_units::detail;
 
diff --git a/test/unit_test/static/quantity_point_test.cpp b/test/unit_test/static/quantity_point_test.cpp
index 71e0457b86..4e8ddf9885 100644
--- a/test/unit_test/static/quantity_point_test.cpp
+++ b/test/unit_test/static/quantity_point_test.cpp
@@ -21,13 +21,19 @@
 // SOFTWARE.
 
 #include "test_tools.h"
+#include <mp-units/quantity_spec_macro.h>
+#include <limits>
+#include <type_traits>
+#include <utility>
+#ifdef MP_UNITS_MODULES
+#include <chrono>
+import mp_units;
+#else
 #include <mp-units/chrono.h>
 #include <mp-units/quantity_point.h>
 #include <mp-units/systems/isq/isq.h>
 #include <mp-units/systems/si/si.h>
-#include <limits>
-#include <type_traits>
-#include <utility>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/quantity_spec_test.cpp b/test/unit_test/static/quantity_spec_test.cpp
index 2183fb5ffa..eb64235306 100644
--- a/test/unit_test/static/quantity_spec_test.cpp
+++ b/test/unit_test/static/quantity_spec_test.cpp
@@ -21,10 +21,14 @@
 // SOFTWARE.
 
 #include "test_tools.h"
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/quantity.h>
 #include <mp-units/quantity_spec.h>
 #include <mp-units/reference.h>
 #include <mp-units/unit.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/quantity_test.cpp b/test/unit_test/static/quantity_test.cpp
index c8fd713bd2..c59ccea11f 100644
--- a/test/unit_test/static/quantity_test.cpp
+++ b/test/unit_test/static/quantity_test.cpp
@@ -21,12 +21,18 @@
 // SOFTWARE.
 
 #include "test_tools.h"
+#include <mp-units/quantity_spec_macro.h>
+#include <limits>
+#include <utility>
+#ifdef MP_UNITS_MODULES
+#include <chrono>
+import mp_units;
+#else
 #include <mp-units/chrono.h>
 #include <mp-units/systems/isq/mechanics.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/si.h>
-#include <limits>
-#include <utility>
+#endif
 
 template<>
 inline constexpr bool mp_units::is_vector<int> = true;
diff --git a/test/unit_test/static/ratio_test.cpp b/test/unit_test/static/ratio_test.cpp
index 5bf9bec08d..fd2113bc00 100644
--- a/test/unit_test/static/ratio_test.cpp
+++ b/test/unit_test/static/ratio_test.cpp
@@ -20,7 +20,11 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/bits/ratio.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/reference_test.cpp b/test/unit_test/static/reference_test.cpp
index 010b77f58b..35bf959fa0 100644
--- a/test/unit_test/static/reference_test.cpp
+++ b/test/unit_test/static/reference_test.cpp
@@ -21,6 +21,9 @@
 // SOFTWARE.
 
 #include "test_tools.h"
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/dimension.h>
 #include <mp-units/quantity.h>
 #include <mp-units/quantity_spec.h>
@@ -28,6 +31,7 @@
 #include <mp-units/system_reference.h>
 #include <mp-units/systems/si/prefixes.h>
 #include <mp-units/unit.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/si_test.cpp b/test/unit_test/static/si_test.cpp
index 69d83096c7..8ce659358d 100644
--- a/test/unit_test/static/si_test.cpp
+++ b/test/unit_test/static/si_test.cpp
@@ -20,8 +20,13 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <type_traits>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/math.h>
 #include <mp-units/systems/si/si.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/symbol_text_test.cpp b/test/unit_test/static/symbol_text_test.cpp
index 0cfa2b4e89..292bbb9eee 100644
--- a/test/unit_test/static/symbol_text_test.cpp
+++ b/test/unit_test/static/symbol_text_test.cpp
@@ -20,7 +20,11 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/bits/symbol_text.h>
+#endif
 
 using namespace mp_units;
 
diff --git a/test/unit_test/static/type_list_test.cpp b/test/unit_test/static/type_list_test.cpp
index 6720ebbbd2..c3d61d5215 100644
--- a/test/unit_test/static/type_list_test.cpp
+++ b/test/unit_test/static/type_list_test.cpp
@@ -20,8 +20,13 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <type_traits>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/bits/external/type_list.h>
 #include <mp-units/bits/external/type_traits.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/typographic_test.cpp b/test/unit_test/static/typographic_test.cpp
index 9a47469ca4..71c713d17b 100644
--- a/test/unit_test/static/typographic_test.cpp
+++ b/test/unit_test/static/typographic_test.cpp
@@ -20,9 +20,13 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/systems/international/international.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/typographic/typographic.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/unit_symbol_test.cpp b/test/unit_test/static/unit_symbol_test.cpp
index a642caaf86..cc129ae950 100644
--- a/test/unit_test/static/unit_symbol_test.cpp
+++ b/test/unit_test/static/unit_symbol_test.cpp
@@ -20,9 +20,13 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/systems/iau/iau.h>
 #include <mp-units/systems/iec80000/iec80000.h>
 #include <mp-units/systems/si/si.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/unit_test.cpp b/test/unit_test/static/unit_test.cpp
index ff5ab4ef83..3c49d3dd9e 100644
--- a/test/unit_test/static/unit_test.cpp
+++ b/test/unit_test/static/unit_test.cpp
@@ -21,11 +21,15 @@
 // SOFTWARE.
 
 #include "test_tools.h"
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/dimension.h>
 #include <mp-units/quantity.h>
 #include <mp-units/reference.h>
 #include <mp-units/systems/si/prefixes.h>
 #include <mp-units/unit.h>
+#endif
 
 namespace {
 
diff --git a/test/unit_test/static/usc_test.cpp b/test/unit_test/static/usc_test.cpp
index b55d02fad8..1c0c5bdf60 100644
--- a/test/unit_test/static/usc_test.cpp
+++ b/test/unit_test/static/usc_test.cpp
@@ -20,10 +20,15 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+#include <mp-units/bits/external/hacks.h>
+#ifdef MP_UNITS_MODULES
+import mp_units;
+#else
 #include <mp-units/systems/isq/mechanics.h>
 #include <mp-units/systems/isq/space_and_time.h>
 #include <mp-units/systems/si/unit_symbols.h>
 #include <mp-units/systems/usc/usc.h>
+#endif
 
 namespace {