diff --git a/.depend b/.depend
index 3cd973067390..313b430cc076 100644
--- a/.depend
+++ b/.depend
@@ -2336,6 +2336,7 @@ bytecomp/bytelink.cmo : \
     utils/consistbl.cmi \
     utils/config.cmi \
     utils/compression.cmi \
+    driver/compenv.cmi \
     file_formats/cmo_format.cmi \
     utils/clflags.cmi \
     utils/ccomp.cmi \
@@ -2355,6 +2356,7 @@ bytecomp/bytelink.cmx : \
     utils/consistbl.cmx \
     utils/config.cmx \
     utils/compression.cmx \
+    driver/compenv.cmx \
     file_formats/cmo_format.cmi \
     utils/clflags.cmx \
     utils/ccomp.cmx \
@@ -2750,6 +2752,7 @@ asmcomp/asmlink.cmo : \
     utils/consistbl.cmi \
     utils/config.cmi \
     middle_end/compilenv.cmi \
+    driver/compenv.cmi \
     file_formats/cmx_format.cmi \
     asmcomp/cmm_helpers.cmi \
     asmcomp/cmm.cmi \
@@ -2771,6 +2774,7 @@ asmcomp/asmlink.cmx : \
     utils/consistbl.cmx \
     utils/config.cmx \
     middle_end/compilenv.cmx \
+    driver/compenv.cmx \
     file_formats/cmx_format.cmi \
     asmcomp/cmm_helpers.cmx \
     asmcomp/cmm.cmx \
diff --git a/Changes b/Changes
index d06707658c06..d273f59ce053 100644
--- a/Changes
+++ b/Changes
@@ -161,6 +161,12 @@ ___________
   runtime assertions.
   (Antonin Décimo, review by Miod Vallat, Gabriel Scherer, and David Allsopp)
 
+- #13???: Added --enable-relative which allows the runtime and the compilers to
+  locate the Standard Library relative to where the binaries themselves,
+  removing the absolute path previously embedded in
+  caml_standard_library_default.
+  (David Allsopp, review by ???)
+
 ### Code generation and optimizations:
 
 - #13014: Enable compile-time option -function-sections on all previously
diff --git a/Makefile b/Makefile
index 2321aed92f8c..14eeac8d6271 100644
--- a/Makefile
+++ b/Makefile
@@ -1429,15 +1429,22 @@ C_LITERAL = $(shell $(SAK) encode-C-literal '$(1)')
 
 runtime/build_config.h: $(ROOTDIR)/Makefile.config $(SAK)
 	$(V_GEN)echo '/* This file is generated from $(ROOTDIR)/Makefile.config */' > $@ && \
-	echo '#define OCAML_STDLIB_DIR $(call C_LITERAL,$(LIBDIR))' >> $@ && \
-	echo '#define HOST "$(HOST)"' >> $@
+	echo '#define OCAML_STDLIB_DIR $(call C_LITERAL,$(LIBDIR))' >> $@
+ifneq "$(LIBDIR_REL)" ""
+	@echo '#define OCAML_STDLIB_DIR_REL $(call C_LITERAL,$(LIBDIR_REL))' >> $@
+endif
+	@echo '#define HOST "$(HOST)"' >> $@
+
+runtime/stdlib.$(O): runtime/build_config.h
 
 ## Runtime libraries and programs
 
-runtime/ocamlrun$(EXE): runtime/prims.$(O) runtime/libcamlrun.$(A)
+runtime/ocamlrun$(EXE): runtime/prims.$(O) runtime/stdlib.$(O) \
+                        runtime/libcamlrun.$(A)
 	$(V_MKEXE)$(MKEXE) -o $@ $^ $(BYTECCLIBS)
 
-runtime/ocamlruns$(EXE): runtime/prims.$(O) runtime/libcamlrun_non_shared.$(A)
+runtime/ocamlruns$(EXE): runtime/prims.$(O) runtime/stdlib.$(O) \
+                         runtime/libcamlrun_non_shared.$(A)
 	$(V_MKEXE)$(call MKEXE_VIA_CC,$@,$^ $(BYTECCLIBS))
 
 runtime/libcamlrun.$(A): $(libcamlrun_OBJECTS)
@@ -1446,13 +1453,15 @@ runtime/libcamlrun.$(A): $(libcamlrun_OBJECTS)
 runtime/libcamlrun_non_shared.$(A): $(libcamlrun_non_shared_OBJECTS)
 	$(V_MKLIB)$(call MKLIB,$@, $^)
 
-runtime/ocamlrund$(EXE): runtime/prims.$(O) runtime/libcamlrund.$(A)
+runtime/ocamlrund$(EXE): runtime/prims.$(O) runtime/stdlib.$(O) \
+                         runtime/libcamlrund.$(A)
 	$(V_MKEXE)$(MKEXE) $(MKEXEDEBUGFLAG) -o $@ $^ $(BYTECCLIBS)
 
 runtime/libcamlrund.$(A): $(libcamlrund_OBJECTS)
 	$(V_MKLIB)$(call MKLIB,$@, $^)
 
-runtime/ocamlruni$(EXE): runtime/prims.$(O) runtime/libcamlruni.$(A)
+runtime/ocamlruni$(EXE): runtime/prims.$(O) runtime/stdlib.$(O) \
+                         runtime/libcamlruni.$(A)
 	$(V_MKEXE)$(MKEXE) -o $@ $^ $(INSTRUMENTED_RUNTIME_LIBS) $(BYTECCLIBS)
 
 runtime/libcamlruni.$(A): $(libcamlruni_OBJECTS)
diff --git a/Makefile.build_config.in b/Makefile.build_config.in
index ae649dcebaa2..32db24485244 100644
--- a/Makefile.build_config.in
+++ b/Makefile.build_config.in
@@ -183,3 +183,5 @@ TSAN=@tsan@
 # Contains TSan-specific runtime files, or nothing if TSan support is
 # disabled
 TSAN_NATIVE_RUNTIME_C_SOURCES = @tsan_native_runtime_c_sources@
+
+RELOCATABLE = @relocatable@
diff --git a/Makefile.common b/Makefile.common
index 1e6a7eff8903..cc659ef824ee 100644
--- a/Makefile.common
+++ b/Makefile.common
@@ -156,6 +156,15 @@ ifeq "$(FUNCTION_SECTIONS)" "true"
 OPTCOMPFLAGS += -function-sections
 endif
 
+ifeq "$(LIBDIR_REL)" ""
+  SET_RELATIVE_STDLIB =
+else
+  SET_RELATIVE_STDLIB = \
+-set-global-string 'caml_standard_library_default=$(LIBDIR_REL)'
+endif
+
+DOTOPT_LINKFLAGS = $(SET_RELATIVE_STDLIB)
+
 # The rule to compile C files
 
 # This rule is similar to GNU make's implicit rule, except that it is more
@@ -360,6 +369,7 @@ $(basename $(notdir $(1)))_NATIVE_LINKFLAGS =
 $(basename $(notdir $(1)))_NATIVE_LINKCMD = \
 $(strip \
   $$(CAMLOPT) $$(OC_COMMON_LINKFLAGS) $$(OC_NATIVE_LINKFLAGS) \
+  $(DOTOPT_LINKFLAGS) \
   $$($(basename $(notdir $(1)))_COMMON_LINKFLAGS) \
   $$($(basename $(notdir $(1)))_NATIVE_LINKFLAGS))
 
diff --git a/asmcomp/asmlink.ml b/asmcomp/asmlink.ml
index b2b74e3568a3..ee98dc304c25 100644
--- a/asmcomp/asmlink.ml
+++ b/asmcomp/asmlink.ml
@@ -335,6 +335,7 @@ let link ~ppf_dump objfiles output_name =
     let obj_infos = List.map read_file objfiles in
     let ldeps = Linkdeps.create ~complete:true in
     let units_tolink = List.fold_right (scan_file ldeps) obj_infos [] in
+    Compenv.set_caml_standard_library_default ();
     (match Linkdeps.check ldeps with
      | None -> ()
      | Some e -> raise (Error (Link_error e)));
diff --git a/bytecomp/bytelink.ml b/bytecomp/bytelink.ml
index 14a680860c28..2b4f119db580 100644
--- a/bytecomp/bytelink.ml
+++ b/bytecomp/bytelink.ml
@@ -780,6 +780,8 @@ let link objfiles output_name =
   Clflags.all_ccopts := !lib_ccopts @ !Clflags.all_ccopts;
                                                    (* put user's opts first *)
   Clflags.dllibs := !lib_dllibs @ !Clflags.dllibs; (* put user's DLLs first *)
+  if !Clflags.custom_runtime then
+    Compenv.set_caml_standard_library_default ();
   if not !Clflags.custom_runtime then begin
     assert (!Clflags.global_string_constants = []);
     link_bytecode tolink output_name true
diff --git a/bytecomp/dll.ml b/bytecomp/dll.ml
index c8b280f9a012..528b963213f6 100644
--- a/bytecomp/dll.ml
+++ b/bytecomp/dll.ml
@@ -143,7 +143,8 @@ let synchronize_primitive num symb =
 let ld_conf_contents () =
   let path = ref [] in
   begin try
-    let ic = open_in (Filename.concat Config.standard_library "ld.conf") in
+    let ic =
+      open_in (Filename.concat Config.standard_library_effective "ld.conf") in
     begin try
       while true do
         path := input_line ic :: !path
diff --git a/configure b/configure
index d5d3d6a0a3d8..fb9f73efa9bf 100755
--- a/configure
+++ b/configure
@@ -785,6 +785,7 @@ build_os
 build_vendor
 build_cpu
 build
+relocatable
 bindir_to_libdir
 ar_supports_response_files
 QS
@@ -3328,6 +3329,7 @@ ocamltest_unix_impl="dummy"
 unix_library=""
 unix_directory=""
 bindir_to_libdir=''
+relocatable=no
 
 # Information about the package
 
@@ -3521,6 +3523,7 @@ LINEAR_MAGIC_NUMBER=Caml1999L035
 
 
 
+
 
 
 ## Generated files
@@ -14953,6 +14956,17 @@ then :
 
 fi
 
+       for ac_header in unistd.h
+do :
+  ac_fn_c_check_header_compile "$LINENO" "unistd.h" "ac_cv_header_unistd_h" "$ac_includes_default"
+if test "x$ac_cv_header_unistd_h" = xyes
+then :
+  printf "%s\n" "#define HAVE_UNISTD_H 1" >>confdefs.h
+ printf "%s\n" "#define HAS_UNISTD 1" >>confdefs.h
+
+fi
+
+done
 ac_fn_c_check_header_compile "$LINENO" "pthread_np.h" "ac_cv_header_pthread_np_h" "$ac_includes_default"
 if test "x$ac_cv_header_pthread_np_h" = xyes
 then :
@@ -20932,6 +20946,7 @@ fi
 if test x"$enable_relative" = "xyes"
 then :
 
+  relocatable=yes
 
   eval "from=\"\$bindir\""
   eval "to=\"\$libdir\""
diff --git a/configure.ac b/configure.ac
index 0ac074aaf852..3ac691760a9c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -84,6 +84,7 @@ ocamltest_unix_impl="dummy"
 unix_library=""
 unix_directory=""
 bindir_to_libdir=''
+relocatable=no
 
 # Information about the package
 
@@ -257,6 +258,7 @@ AC_SUBST([ocaml_libdir])
 AC_SUBST([QS])
 AC_SUBST([ar_supports_response_files])
 AC_SUBST([bindir_to_libdir])
+AC_SUBST([relocatable])
 
 ## Generated files
 
@@ -1169,6 +1171,7 @@ AS_CASE([$host],
   [AC_CHECK_HEADERS([unistd.h],[AC_DEFINE([HAS_UNISTD], [1])])])
 
 AC_CHECK_HEADER([math.h])
+AC_CHECK_HEADERS([unistd.h],[AC_DEFINE([HAS_UNISTD])])
 AC_CHECK_HEADER([pthread_np.h],[AC_DEFINE([HAS_PTHREAD_NP_H], [1])])
 AC_CHECK_HEADER([dirent.h], [AC_DEFINE([HAS_DIRENT], [1])], [],
   [#include <sys/types.h>])
@@ -2645,6 +2648,7 @@ AS_IF([test x"$mandir" = x'${datarootdir}/man'],
   [mandir='${prefix}/man'])
 
 AS_IF([test x"$enable_relative" = "xyes"],[
+  relocatable=yes
   OCAML_COMPUTE_BINDIR_TO_LIBDIR([bindir],[libdir],[bindir_to_libdir])
   dnl Tests for the OCAML_COMPUTE_BINDIR_TO_LIBDIR macro
   dnl OCAML_COMPUTE_BINDIR_TO_LIBDIR_TESTS
diff --git a/driver/compenv.ml b/driver/compenv.ml
index 921c05655001..7fe010e52ab8 100644
--- a/driver/compenv.ml
+++ b/driver/compenv.ml
@@ -732,3 +732,10 @@ let parse_arguments ?(current=ref 0) argv f program =
         Printf.sprintf "Usage: %s <options> <files>\nOptions are:" program in
       Printf.printf "%s\n%s" help_msg err_msg;
       raise (Exit_with_status 0)
+
+let set_caml_standard_library_default () =
+  let symbol = "caml_standard_library_default" in
+  if not (List.exists (fun (name, _) -> name = symbol)
+                      !global_string_constants) then
+    global_string_constants :=
+      (symbol, Config.standard_library_effective) :: !global_string_constants
diff --git a/driver/compenv.mli b/driver/compenv.mli
index a5958554e76e..12d3bd9274a1 100644
--- a/driver/compenv.mli
+++ b/driver/compenv.mli
@@ -76,3 +76,7 @@ val process_deferred_actions :
 *)
 val parse_arguments : ?current:(int ref)
       -> string array ref -> Arg.anon_fun -> string -> unit
+
+(** Adds caml_standard_library_default to {!Clflags.global_string_constants}
+    if it isn't already present. *)
+val set_caml_standard_library_default: unit -> unit
diff --git a/runtime/caml/dynlink.h b/runtime/caml/dynlink.h
index d5f7170e6fcb..c8a1d88cb0ba 100644
--- a/runtime/caml/dynlink.h
+++ b/runtime/caml/dynlink.h
@@ -41,9 +41,6 @@ extern void caml_build_primitive_table_builtin(void);
 /* Unload all the previously loaded shared libraries */
 extern void caml_free_shared_libs(void);
 
-/* Return the effective location of the standard library */
-extern char_os * caml_get_stdlib_location(void);
-
 /* Parse ld.conf and add the lines read to caml_shared_libs_path */
 extern char_os * caml_parse_ld_conf(void);
 
diff --git a/runtime/caml/osdeps.h b/runtime/caml/osdeps.h
index 6d414a325174..9e6a217c8268 100644
--- a/runtime/caml/osdeps.h
+++ b/runtime/caml/osdeps.h
@@ -142,6 +142,14 @@ CAMLextern clock_t caml_win32_clock(void);
 
 CAMLextern value caml_win32_xdg_defaults(void);
 
+#define CAML_DIR_SEP T("\\")
+#define Is_dir_separator(c) (c == '\\' || c == '/')
+
+#else
+
+#define CAML_DIR_SEP "/"
+#define Is_dir_separator(c) (c == '/')
+
 #endif /* _WIN32 */
 
 /* Returns the current value of a counter that increments once per nanosecond.
@@ -155,6 +163,18 @@ extern uint64_t caml_time_counter(void);
 
 extern void caml_init_os_params(void);
 
+/* True if:
+   - dir equals "."
+   - dir equals ".."
+   - dir begins "./"
+   - dir begins "../"
+   The tests for null avoid the need to call strlen_os. */
+#define Is_relative_dir(dir) \
+  (dir[0] == '.' \
+   && (dir[1] == 0 \
+       || Is_dir_separator(dir[1]) \
+       || (dir[1] == '.' && (dir[2] == 0 || Is_dir_separator(dir[2])))))
+
 #endif /* CAML_INTERNALS */
 
 #ifdef _WIN32
diff --git a/runtime/caml/s.h.in b/runtime/caml/s.h.in
index bc6ced458da6..8c6b6b6af999 100644
--- a/runtime/caml/s.h.in
+++ b/runtime/caml/s.h.in
@@ -112,6 +112,10 @@
 
 /* Define HAS_UNISTD if you have /usr/include/unistd.h. */
 
+#undef HAS_LIBGEN_H
+
+/* Define HAS_LIBGEN_H if you have /usr/include/libgen.h. */
+
 #undef HAS_DIRENT
 
 /* Define HAS_DIRENT if you have /usr/include/dirent.h and the result of
diff --git a/runtime/caml/sys.h b/runtime/caml/sys.h
index b6e6af870311..23f5671e988d 100644
--- a/runtime/caml/sys.h
+++ b/runtime/caml/sys.h
@@ -34,9 +34,15 @@ CAMLnoret CAMLextern void caml_sys_io_error (value);
 
 CAMLextern double caml_sys_time_unboxed(value);
 CAMLextern void caml_sys_init (char_os * exe_name, char_os ** argv);
+CAMLextern void caml_locate_standard_library (const char_os *);
 
 CAMLnoret CAMLextern void caml_do_exit (int);
 
+extern char_os * caml_standard_library_default;
+extern char_os * caml_standard_library_relative;
+extern char_os * caml_standard_library;
+extern char_os *_Atomic caml_relative_root_dir;
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/runtime/dynlink.c b/runtime/dynlink.c
index c06f8adb9aac..28579e175d5e 100644
--- a/runtime/dynlink.c
+++ b/runtime/dynlink.c
@@ -40,6 +40,7 @@
 #include "caml/signals.h"
 #include "caml/intext.h"
 #include "caml/startup.h"
+#include "caml/sys.h"
 
 #include "build_config.h"
 
@@ -88,7 +89,7 @@ CAMLexport char_os * caml_get_stdlib_location(void)
   char_os * stdlib;
   stdlib = caml_secure_getenv(T("OCAMLLIB"));
   if (stdlib == NULL) stdlib = caml_secure_getenv(T("CAMLLIB"));
-  if (stdlib == NULL) stdlib = OCAML_STDLIB_DIR;
+  if (stdlib == NULL) stdlib = caml_standard_library;
   return stdlib;
 }
 
diff --git a/runtime/startup_byt.c b/runtime/startup_byt.c
index ffb4eb0bebdd..486b83662b93 100644
--- a/runtime/startup_byt.c
+++ b/runtime/startup_byt.c
@@ -383,9 +383,7 @@ static void do_print_config(void)
   /* Print the runtime configuration */
   printf("version: %s\n", OCAML_VERSION_STRING);
   printf("standard_library_default: %s\n",
-         caml_stat_strdup_of_os(OCAML_STDLIB_DIR));
-  printf("standard_library: %s\n",
-         caml_stat_strdup_of_os(caml_get_stdlib_location()));
+         caml_stat_strdup_of_os(caml_standard_library_default));
   printf("int_size: %d\n", 8 * (int)sizeof(value));
   printf("word_size: %d\n", 8 * (int)sizeof(value) - 1);
   printf("os_type: %s\n", OCAML_OS_TYPE);
@@ -486,11 +484,14 @@ CAMLexport void caml_main(char_os **argv)
      With -custom, we have an executable that is ocamlrun itself
      concatenated with the bytecode.  So, if the attempt with argv[0]
      failed, it is worth trying again with executable_name. */
-  if (fd < 0 && (proc_self_exe = caml_executable_name()) != NULL) {
+  proc_self_exe = caml_executable_name();
+  if (fd < 0 && proc_self_exe != NULL) {
     exe_name = proc_self_exe;
     fd = caml_attempt_open(&exe_name, &trail, 0);
   }
 
+  caml_locate_standard_library(proc_self_exe ? proc_self_exe : exe_name);
+
   if (fd < 0) {
     pos = parse_command_line(argv);
     if (caml_params->print_config) {
@@ -622,6 +623,8 @@ CAMLexport value caml_startup_code_exn(
   exe_name = caml_executable_name();
   if (exe_name == NULL) exe_name = caml_search_exe_in_path(argv[0]);
 
+  caml_locate_standard_library(exe_name);
+
   Caml_state->external_raise = NULL;
   /* Setup signal handling */
   caml_init_signals();
diff --git a/runtime/stdlib.c b/runtime/stdlib.c
new file mode 100644
index 000000000000..0be10ae51df5
--- /dev/null
+++ b/runtime/stdlib.c
@@ -0,0 +1,22 @@
+/**************************************************************************/
+/*                                                                        */
+/*                                 OCaml                                  */
+/*                                                                        */
+/*                 David Allsopp, OCaml Labs, Cambridge.                  */
+/*                                                                        */
+/*   Copyright 2021 David Allsopp Ltd.                                    */
+/*                                                                        */
+/*   All rights reserved.  This file is distributed under the terms of    */
+/*   the GNU Lesser General Public License version 2.1, with the          */
+/*   special exception on linking described in the file LICENSE.          */
+/*                                                                        */
+/**************************************************************************/
+
+#include "caml/misc.h"
+#include "build_config.h"
+
+#if defined(OCAML_STDLIB_DIR_REL)
+char_os * caml_standard_library_default = OCAML_STDLIB_DIR_REL;
+#else
+char_os * caml_standard_library_default = OCAML_STDLIB_DIR;
+#endif
diff --git a/runtime/sys.c b/runtime/sys.c
index 3356664ecdbd..d105d5357a2f 100644
--- a/runtime/sys.c
+++ b/runtime/sys.c
@@ -67,6 +67,9 @@
 #include "caml/major_gc.h"
 #include "caml/shared_heap.h"
 
+char_os * caml_standard_library = NULL;
+char_os *_Atomic caml_relative_root_dir = NULL;
+
 CAMLexport char * caml_strerror(int errnum, char * buf, size_t buflen)
 {
 #ifdef _WIN32
@@ -700,6 +703,30 @@ CAMLprim value caml_sys_const_backend_type(value unit)
 {
   return Val_int(1); /* Bytecode backed */
 }
+
+CAMLprim value caml_sys_get_stdlib_dirs(value unit)
+{
+  CAMLparam0();
+  CAMLlocal4(result, def, eff, root_dir);
+#ifdef NATIVE_CODE
+  if (caml_standard_library == NULL)
+    caml_locate_standard_library(caml_params->exe_name);
+#endif
+  def = caml_copy_string_of_os(caml_standard_library_default);
+  if (caml_relative_root_dir != NULL) {
+    root_dir = caml_copy_string_of_os(caml_relative_root_dir);
+    root_dir = caml_alloc_some(root_dir);
+  } else {
+    root_dir = Val_none;
+  }
+  eff = caml_copy_string_of_os(caml_standard_library);
+  result = caml_alloc_small(3, 0);
+  Field(result, 0) = def;
+  Field(result, 1) = eff;
+  Field(result, 2) = root_dir;
+  CAMLreturn(result);
+}
+
 CAMLprim value caml_sys_get_config(value unit)
 {
   CAMLparam0 ();   /* unit is unused */
diff --git a/runtime/unix.c b/runtime/unix.c
index e19d5a26a86d..110c55c29dbb 100644
--- a/runtime/unix.c
+++ b/runtime/unix.c
@@ -54,6 +54,9 @@
 #else
 #include <sys/dir.h>
 #endif
+#ifdef HAS_LIBGEN_H
+#include <libgen.h>
+#endif
 #ifdef __APPLE__
 #include <mach-o/dyld.h>
 #endif
@@ -541,3 +544,70 @@ void caml_plat_mem_unmap(void* mem, uintnat size)
   if (munmap(mem, size) != 0)
     CAMLassert(0);
 }
+
+static char * caml_dirname (const char * path)
+{
+#ifdef HAS_LIBGEN_H
+  char *dir, *res;
+  dir = caml_stat_strdup(path);
+  res = caml_stat_strdup(dirname(dir));
+  caml_stat_free(dir);
+  return res;
+#else
+  /* See Filename.generic_dirname */
+  size_t n = strlen(path) - 1;
+  char *res;
+  if (n < 0) /* path is "" */
+    return caml_stat_strdup(".");
+  while (n >= 0 && path[n] == '/')
+    n--;
+  if (n < 0) /* path is entirely slashes */
+    return caml_stat_strdup("/");
+  while (n >= 0 && path[n] != '/')
+    n--;
+  if (n < 0) /* path is relative */
+    return caml_stat_strdup(".");
+  while (n >= 0 && path[n] == '/')
+    n--;
+  if (n < 0) /* path is a file at root */
+    return caml_stat_strdup("/");
+  /* n is the _index_ of the last character of the dirname */
+  res = caml_stat_alloc(n + 2);
+  memcpy(res, path, n + 1);
+  res[n + 1] = 0;
+  return res;
+#endif
+}
+
+CAMLextern void caml_locate_standard_library (const char *exe_name)
+{
+  if (Is_relative_dir(caml_standard_library_default)) {
+    char * candidate = NULL;
+    char * root = caml_dirname(exe_name);
+    /* Determine the standard library default relative to exe_name */
+    if (!atomic_compare_exchange_weak(&caml_relative_root_dir,
+                                      &candidate, root)) {
+      caml_stat_free(root);
+    } else {
+      candidate = caml_stat_strconcat_os(3, caml_relative_root_dir,
+                                            CAML_DIR_SEP,
+                                            caml_standard_library_default);
+#ifndef HAS_REALPATH
+      caml_standard_library = candidate;
+#else
+      char * resolved_candidate = realpath(candidate, NULL);
+      /* If realpath fails, use the non-normalised path for error messages. */
+      if (resolved_candidate == NULL) {
+        caml_standard_library = candidate;
+      } else {
+        caml_stat_free(candidate);
+        /* caml_realpath uses malloc */
+        caml_standard_library = caml_stat_strdup_os(resolved_candidate);
+        free(resolved_candidate);
+      }
+#endif
+    }
+  } else {
+    caml_standard_library = caml_standard_library_default;
+  }
+}
diff --git a/runtime/win32.c b/runtime/win32.c
index 5b324da96189..85e0a2731f37 100644
--- a/runtime/win32.c
+++ b/runtime/win32.c
@@ -41,6 +41,7 @@
 #include <errno.h>
 #include <string.h>
 #include <signal.h>
+#include <wchar.h>
 #include "caml/alloc.h"
 #include "caml/codefrag.h"
 #include "caml/fail.h"
@@ -1291,3 +1292,79 @@ value caml_win32_xdg_defaults(void)
 
   CAMLreturn(result);
 }
+
+CAMLextern void caml_locate_standard_library (const wchar_t *exe_name)
+{
+  if (Is_relative_dir(caml_standard_library_default)) {
+    LPWSTR root, basename, candidate = NULL;
+    DWORD buf_len, l;
+    HANDLE h;
+    l = GetFullPathName(exe_name, 0, NULL, NULL);
+    if (l == 0) {
+      /* Impossible thing: the path returned by GetModuleFileName can't be
+         parsed by GetFullPathName */
+      caml_standard_library = caml_standard_library_default;
+      return;
+    }
+again1:
+    CAMLassert(l != 0);
+    buf_len = l;
+    root = caml_stat_alloc(buf_len * sizeof(wchar_t));
+    l = GetFullPathName(exe_name, buf_len, root, &basename);
+    if (l > buf_len) {
+      caml_stat_free(root);
+      goto again1;
+    }
+    CAMLassert(basename != root && *(basename - 1) == '/');
+    /* Make root the dirname */
+    *(basename - 1) = 0;
+    /* Determine the standard library default relative to exe_name */
+    if (!atomic_compare_exchange_weak(&caml_relative_root_dir,
+                                      &candidate, root)) {
+      caml_stat_free(root);
+    } else {
+      LPWSTR resolved_candidate = NULL;
+      candidate = caml_stat_strconcat_os(3, caml_relative_root_dir,
+                                            CAML_DIR_SEP,
+                                            caml_standard_library_default);
+      h = CreateFile(candidate, 0,
+                     FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+                     NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
+      if (h != INVALID_HANDLE_VALUE) {
+        l = GetFinalPathNameByHandle(h, NULL, 0,
+                                     FILE_NAME_NORMALIZED | VOLUME_NAME_DOS);
+again2:
+        buf_len = l;
+        resolved_candidate = caml_stat_alloc(buf_len * sizeof(wchar_t));
+        l = GetFinalPathNameByHandle(h, resolved_candidate, buf_len,
+                                     FILE_NAME_NORMALIZED | VOLUME_NAME_DOS);
+        if (l > buf_len) {
+          caml_stat_free(resolved_candidate);
+          goto again2;
+        }
+        /* GetFinalPathNameByHandle always returns \\?\ which needs stripping.
+           UNC paths are returned as \\?\UNC\ - in this case, reuse the \\ from
+           \\?\. */
+        CAMLassert(l > 4 && resolved_candidate[0] == '\\'
+                         && resolved_candidate[1] == '\\'
+                         && resolved_candidate[2] == '?'
+                         && resolved_candidate[3] == '\\');
+        if (l >= 8 && resolved_candidate[4] == 'U'
+                   && resolved_candidate[5] == 'N'
+                   && resolved_candidate[6] == 'C'
+                   && resolved_candidate[7] == '\\')
+          wmemmove_s(resolved_candidate + 2, l - 1,
+                     resolved_candidate + 8, l - 7);
+        else
+          wmemmove_s(resolved_candidate, l + 1,
+                     resolved_candidate + 4, l - 3);
+        caml_stat_free(candidate);
+        caml_standard_library = resolved_candidate;
+      } else {
+        caml_standard_library = candidate;
+      }
+    }
+  } else {
+    caml_standard_library = caml_standard_library_default;
+  }
+}
diff --git a/tools/ocamlmklib.ml b/tools/ocamlmklib.ml
index f6b2a2d16ec9..1082a208d3c7 100644
--- a/tools/ocamlmklib.ml
+++ b/tools/ocamlmklib.ml
@@ -25,10 +25,8 @@ let mklib out files opts =
   Printf.sprintf "link -lib -nologo %s-out:%s %s %s" machine out opts files
   else Printf.sprintf "%s rcs %s %s %s" Config.ar out opts files
 
-(* PR#4783: under Windows, don't use absolute paths because we do
-   not know where the binary distribution will be installed. *)
 let compiler_path name =
-  if Sys.os_type = "Win32" then name else Filename.concat Config.bindir name
+  Filename.concat Config.bindir name
 
 let bytecode_objs = ref []  (* .cmo,.cma,.ml,.mli files to pass to ocamlc *)
 and native_objs = ref []    (* .cmx,.ml,.mli files to pass to ocamlopt *)
diff --git a/utils/config.common.ml.in b/utils/config.common.ml.in
index 3603fe6c60c7..459b18d9d9e7 100644
--- a/utils/config.common.ml.in
+++ b/utils/config.common.ml.in
@@ -27,7 +27,7 @@ let standard_library =
   try
     Sys.getenv "CAMLLIB"
   with Not_found ->
-    standard_library_default
+    standard_library_effective
 
 let exec_magic_number = {magic|@EXEC_MAGIC_NUMBER@|magic}
     (* exec_magic_number is duplicated in runtime/caml/exec.h *)
@@ -73,7 +73,7 @@ let configuration_variables () =
   let p_bool x v = (x, Bool v) in
 [
   p "version" version;
-  p "standard_library_default" standard_library_default;
+  p "standard_library_default" standard_library_effective;
   p "standard_library" standard_library;
   p "ccomp_type" ccomp_type;
   p "c_compiler" c_compiler;
diff --git a/utils/config.fixed.ml b/utils/config.fixed.ml
index 49194b9518c3..16d2cc7c19d1 100644
--- a/utils/config.fixed.ml
+++ b/utils/config.fixed.ml
@@ -22,6 +22,8 @@ let boot_cannot_call s = "/ The boot compiler should not call " ^ s
 
 let bindir = "/tmp"
 let standard_library_default = "/tmp"
+let standard_library_effective = "/tmp"
+let standard_library_relative = false
 let ccomp_type = "n/a"
 let c_compiler = boot_cannot_call "the C compiler"
 let c_output_obj = ""
diff --git a/utils/config.generated.ml.in b/utils/config.generated.ml.in
index 46f8d611ce9a..46ab22ccef56 100644
--- a/utils/config.generated.ml.in
+++ b/utils/config.generated.ml.in
@@ -18,9 +18,23 @@
 (* This file is included in config_main.ml during the build rather
    than compiled on its own *)
 
-let bindir = {@QS@|@ocaml_bindir@|@QS@}
-
-let standard_library_default = {@QS@|@ocaml_libdir@|@QS@}
+external stdlib_dirs : unit -> string * string * string option
+   = "caml_sys_get_stdlib_dirs"
+
+let (standard_library_default,
+     standard_library_effective,
+     relative_root_dir) = stdlib_dirs ()
+
+let bindir =
+  let default =
+    if {@QS@|@bindir_to_libdir@|@QS@} = "" then
+      {@QS@|@bindir@|@QS@}
+    else
+      ""
+  in
+  Option.value ~default relative_root_dir
+
+let standard_library_relative = relative_root_dir <> None
 
 let ccomp_type = {@QS@|@ccomptype@|@QS@}
 let c_compiler = {@QS@|@CC@|@QS@}
diff --git a/utils/config.mli b/utils/config.mli
index e9b24a18d905..d179a602e6b3 100644
--- a/utils/config.mli
+++ b/utils/config.mli
@@ -24,10 +24,31 @@ val version: string
 (** The current version number of the system *)
 
 val bindir: string
-(** The directory containing the binary programs *)
+(** The directory containing the binary programs. If the compiler was configured
+    with [--enable-relative] then this will be the directory containing the
+    currently executing runtime. *)
+
+val standard_library_default: string
+(** The configured value for the directory containing the standard libraries.
+    May be a relative path if the compiler was configured with
+    [--enable-relative].
+
+    @since 5.1 *)
+
+val standard_library_effective: string
+(** The standard library directory, computed taking {!standard_library_relative}
+    and {!standard_library_default} into account, but not taking CAMLLIB or
+    OCAMLLIB into account.
+
+    @since 5.1 *)
+
+val standard_library_relative: bool
+(** Whether {!standard_library_effective} is computed relative to the runtime.
+
+    @since 5.1 *)
 
 val standard_library: string
-(** The directory containing the standard libraries *)
+(** The effective directory containing the standard libraries. *)
 
 val ccomp_type: string
 (** The "kind" of the C compiler, assembler and linker used: one of