diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index fb052f7928..6d87e8379e 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -70,11 +70,19 @@ jobs:
             task: 'ci-compile'
             python-version-short: '3.8'
             python-version: '3.8.10'
+          - name: 'Lint Checks (black, flake8, etc.)'
+            task: 'ci-checks'
+            python-version-short: '3.9'
+            python-version: '3.9.14'
+          - name: 'Compile (pip deps, pylint, etc.)'
+            task: 'ci-compile'
+            python-version-short: '3.9'
+            python-version: '3.9.14'
 
     env:
       TASK: '${{ matrix.task }}'
       COLUMNS: '120'
-      PYLINT_CONCURRENCY: '4'
+      PYLINT_CONCURRENCY: '6'
     steps:
       - name: Checkout repository
         uses: actions/checkout@v2
@@ -174,6 +182,18 @@ jobs:
             nosetests_node_index: 1
             python-version-short: '3.8'
             python-version: '3.8.10'
+          - name: 'Unit Tests (chunk 1)'
+            task: 'ci-unit'
+            nosetests_node_total: 2
+            nosetests_node_index: 0
+            python-version-short: '3.9'
+            python-version: '3.9.14'
+          - name: 'Unit Tests (chunk 2)'
+            task: 'ci-unit'
+            nosetests_node_total: 2
+            nosetests_node_index: 1
+            python-version-short: '3.9'
+            python-version: '3.9.14'
           # This job is slow so we only run in on a daily basis
           # - name: 'Micro Benchmarks'
           #   task: 'micro-benchmarks'
@@ -359,6 +379,24 @@ jobs:
             nosetests_node_index: 1
             python-version-short: '3.8'
             python-version: '3.8.10'
+          - name: 'Pack Tests'
+            task: 'ci-packs-tests'
+            nosetests_node_total: 1
+            nosetests_node_index: 0
+            python-version-short: '3.9'
+            python-version: '3.9.14'
+          - name: 'Integration Tests (chunk 1)'
+            task: 'ci-integration'
+            nosetests_node_total: 2
+            nosetests_node_index: 0
+            python-version-short: '3.9'
+            python-version: '3.9.14'
+          - name: 'Integration Tests (chunk 2)'
+            task: 'ci-integration'
+            nosetests_node_total: 2
+            nosetests_node_index: 1
+            python-version-short: '3.9'
+            python-version: '3.9.14'
     services:
       mongo:
         image: mongo:4.4
diff --git a/.github/workflows/microbenchmarks.yaml b/.github/workflows/microbenchmarks.yaml
index fcc7b5cca0..9477b256f8 100644
--- a/.github/workflows/microbenchmarks.yaml
+++ b/.github/workflows/microbenchmarks.yaml
@@ -46,6 +46,12 @@ jobs:
             nosetests_node_index: 0
             python-version-short: '3.8'
             python-version: '3.8.10'
+          - name: 'Microbenchmarks'
+            task: 'micro-benchmarks'
+            nosetests_node_total: 1
+            nosetests_node_index: 0
+            python-version-short: '3.9'
+            python-version: '3.9.14'
     services:
       mongo:
         image: mongo:4.4
diff --git a/.github/workflows/orquesta-integration-tests.yaml b/.github/workflows/orquesta-integration-tests.yaml
index 5e0a4ebeef..84913a1cd3 100644
--- a/.github/workflows/orquesta-integration-tests.yaml
+++ b/.github/workflows/orquesta-integration-tests.yaml
@@ -67,6 +67,12 @@ jobs:
             nosetests_node_index: 0
             python-version-short: '3.8'
             python-version: '3.8.10'
+          - name: 'Integration Tests (Orquesta)'
+            task: 'ci-orquesta'
+            nosetests_node_total: 1
+            nosetests_node_index: 0
+            python-version-short: '3.9'
+            python-version: '3.9.14'
     services:
       mongo:
         image: mongo:4.4
diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index 334479b702..172c0cd64d 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -38,6 +38,9 @@ jobs:
           - name: 'Test (pants runs: pytest)'
             python-version-short: '3.8'
             python-version: '3.8.10'
+          - name: 'Test (pants runs: pytest)'
+            python-version-short: '3.9'
+            python-version: '3.9.14'
 
     services:
       mongo:
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index ad8cb12637..a267a04fed 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -40,6 +40,9 @@ Added
 * Expose environment variable ST2_ACTION_DEBUG to all StackStorm actions.
   Contributed by @maxfactor1
 
+* Python 3.9 support. #5730
+  Contributed by Amanda McGuinness (@amanda11 intive)
+
 Changed
 ~~~~~~~
 * Remove `distutils` dependencies across the project. #5992
diff --git a/lockfiles/st2.lock b/lockfiles/st2.lock
index 852a04be5b..1d97f6325d 100644
--- a/lockfiles/st2.lock
+++ b/lockfiles/st2.lock
@@ -6,7 +6,7 @@
 // {
 //   "version": 3,
 //   "valid_for_interpreter_constraints": [
-//     "CPython<3.9,>=3.6"
+//     "CPython<3.10,>=3.6"
 //   ],
 //   "generated_with_requirements": [
 //     "PyYAML",
@@ -5089,7 +5089,7 @@
     "zstandard"
   ],
   "requires_python": [
-    "<3.9,>=3.6"
+    "<3.10,>=3.6"
   ],
   "resolver_version": "pip-2020-resolver",
   "style": "universal",
diff --git a/pants.toml b/pants.toml
index 42f4a886e9..04435830d0 100644
--- a/pants.toml
+++ b/pants.toml
@@ -108,8 +108,8 @@ enable_resolves = true
 default_resolve = "st2"
 interpreter_constraints = [
   # python_distributions needs a single constraint (vs one line per python version).
-  # officially, we exclude 3.7 support, but that adds unnecessary complexity: "CPython>=3.6,!=3.7.*,<3.9",
-  "CPython>=3.6,<3.9",
+  # officially, we exclude 3.7 support, but that adds unnecessary complexity: "CPython>=3.6,!=3.7.*,<3.10",
+  "CPython>=3.6,<3.10",
   # NB: constraints for tools defined below
 ]
 
diff --git a/pylint_plugins/api_models.py b/pylint_plugins/api_models.py
index a5b3cf00bf..d2b7d7e9b3 100644
--- a/pylint_plugins/api_models.py
+++ b/pylint_plugins/api_models.py
@@ -147,11 +147,24 @@ def transform(cls: nodes.ClassDef):
                 if (
                     isinstance(target, nodes.Subscript)
                     and target.value.value.name == "schema"
-                    and target.value.slice.value.value == "properties"
                 ):
-                    property_name_node = target.slice.value
+                    if (
+                        isinstance(target.value.slice.value, nodes.Const)
+                        and target.value.slice.value.value == "properties"
+                    ):
+                        # python <3.9
+                        property_name_node = target.slice.value
+                    elif (
+                        isinstance(target.value.slice, nodes.Const)
+                        and target.value.slice.value == "properties"
+                    ):
+                        # python 3.9+
+                        property_name_node = target.slice
+                    else:
+                        # not schema["properties"]
+                        continue
                 else:
-                    # not schema["properties"]
+                    # not schema[...]
                     continue
             except AttributeError:
                 continue
@@ -197,7 +210,12 @@ def transform(cls: nodes.ClassDef):
         #   schema = {"properties": {"action": REQUIRED_ATTR_SCHEMAS["action"]}}
         if isinstance(property_data_node, nodes.Subscript):
             var_name = property_data_node.value.name
-            subscript = property_data_node.slice.value.value
+            if isinstance(property_data_node.slice.value, nodes.Const):  # python <3.9
+                subscript = property_data_node.slice.value.value
+            elif isinstance(property_data_node.slice, nodes.Const):  # python 3.9+
+                subscript = property_data_node.slice.value
+            else:
+                continue
 
             # lookup var by name (assume its at module level)
             var_node = next(cls.root().igetattr(var_name))