diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index a7d26b8edf..2e4ca2fb0b 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -23,19 +23,17 @@ on:
   #  - cron:  '0 0 * * *'
 
 jobs:
-  unit-tests:
-    name: 'Unit Tests (pants runs: pytest) - Python ${{ matrix.python-version-short }}'
+  pants-plugins-tests:
+    name: 'Pants Plugins Tests (pants runs: pytest) - Python ${{ matrix.python.version-short }}'
     runs-on: ubuntu-20.04
     strategy:
       fail-fast: false
       matrix:
         # NOTE: We need to use full Python version as part of Python deps cache key otherwise
         # setup virtualenv step will fail.
-        include:
-          - python-version-short: '3.8'
-            python-version: '3.8.10'
-          - python-version-short: '3.9'
-            python-version: '3.9.14'
+        python:
+          # Pants itself uses only 3.9
+          - {version-short: '3.9', version: '3.9.14'}
 
     services:
       mongo:
@@ -85,11 +83,11 @@ jobs:
           git submodule foreach 'git fetch --all --tags'
           git submodule foreach 'git tag'
 
-      - name: 'Set up Python (${{ matrix.python-version }})'
+      - name: 'Set up Python (${{ matrix.python.version }})'
         id: python
         uses: actions/setup-python@v5
         with:
-          python-version: '${{ matrix.python-version }}'
+          python-version: '${{ matrix.python.version }}'
 
       - name: Cache and Install APT Dependencies
         uses: ./.github/actions/apt-packages
@@ -98,16 +96,102 @@ jobs:
         uses: ./.github/actions/init-pants
         with:
           # To ignore a bad cache, bump the cache* integer.
-          gha-cache-key: cache0-py${{ matrix.python-version }}
+          gha-cache-key: cache0-py${{ matrix.python.version }}
 
       - name: Test pants-plugins
-        if: ${{ matrix.python-version-short == '3.9' }}
         env:
           # Github Actions uses the 'runner' user, so use that instead of stanley.
           ST2TESTS_SYSTEM_USER: 'runner'
         run: |
           pants test pants-plugins/::
 
+      - name: Upload pants log
+        uses: actions/upload-artifact@v4
+        with:
+          name: pants-log-py${{ matrix.python.version }}-pants-plugins-tests
+          path: .pants.d/pants.log
+        if: always()  # We want the log even on failures.
+
+  unit-tests:
+    name: 'Unit Tests Shard ${{ matrix.shard.k }}/${{ matrix.shard.n }} (pants runs: pytest) - Python ${{ matrix.python.version-short }}'
+    runs-on: ubuntu-20.04
+    strategy:
+      fail-fast: false
+      matrix:
+        # NOTE: We need to use full Python version as part of Python deps cache key otherwise
+        # setup virtualenv step will fail.
+        python:
+          - {version-short: '3.8', version: '3.8.10'}
+          - {version-short: '3.9', version: '3.9.14'}
+        shard:
+          # Sharding of tests is handled by pants:
+          # https://www.pantsbuild.org/stable/docs/using-pants/advanced-target-selection#sharding-the-input-targets
+          - {k: '0', n: '2'}
+          - {k: '1', n: '2'}
+
+    services:
+      mongo:
+        image: mongo:7.0
+        ports:
+          - 27017:27017
+
+      rabbitmq:
+        image: rabbitmq:3.8-management
+        options: >-
+          --name rabbitmq
+        ports:
+          - 5671:5671/tcp   # AMQP SSL port
+          - 5672:5672/tcp   # AMQP standard port
+          - 15672:15672/tcp # Management: HTTP, CLI
+
+      redis:
+         # Docker Hub image
+         image: redis
+         # Set health checks to wait until redis has started
+         options: >-
+           --name "redis"
+           --health-cmd "redis-cli ping"
+           --health-interval 10s
+           --health-timeout 5s
+           --health-retries 5
+         ports:
+           - 6379:6379/tcp
+
+    env:
+      COLUMNS: '120'
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          # a test uses a submodule, and pants needs access to it to calculate deps.
+          submodules: 'recursive'
+          # sadly, the submodule will only have fetch-depth=1, which is what we want
+          # for st2.git, but not for the submodules. We still want actions/checkout
+          # to do the initial checkout, however, so that it adds auth for fetching
+          # in the submodule.
+
+      - name: Fetch repository submodules
+        run: |
+          git submodule status
+          git submodule foreach 'git fetch --all --tags'
+          git submodule foreach 'git tag'
+
+      - name: 'Set up Python (${{ matrix.python.version }})'
+        id: python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '${{ matrix.python.version }}'
+
+      - name: Cache and Install APT Dependencies
+        uses: ./.github/actions/apt-packages
+
+      - name: Initialize Pants and its GHA caches
+        uses: ./.github/actions/init-pants
+        with:
+          # To ignore a bad cache, bump the cache* integer.
+          gha-cache-key: cache0-py${{ matrix.python.version }}
+
       - name: Unit Tests
         env:
           # Github Actions uses the 'runner' user, so use that instead of stanley.
@@ -117,28 +201,27 @@ jobs:
           --python-bootstrap-search-path=[]
           --python-bootstrap-search-path=${{ steps.python.outputs.python-path }}
           --tag=unit
+          --test-shard=${{ matrix.shard.k }}/${{ matrix.shard.n }}
           test '::'
 
       - name: Upload pants log
         uses: actions/upload-artifact@v4
         with:
-          name: pants-log-py${{ matrix.python-version }}
+          name: pants-log-py${{ matrix.python.version }}-unit-tests-shard-${{ matrix.shard.k }}_${{ matrix.shard.n }}
           path: .pants.d/pants.log
         if: always()  # We want the log even on failures.
 
   pack-tests:
-    name: 'Pack Tests (pants runs: pytest) - Python ${{ matrix.python-version-short }}'
+    name: 'Pack Tests (pants runs: pytest) - Python ${{ matrix.python.version-short }}'
     runs-on: ubuntu-20.04
     strategy:
       fail-fast: false
       matrix:
         # NOTE: We need to use full Python version as part of Python deps cache key otherwise
         # setup virtualenv step will fail.
-        include:
-          - python-version-short: '3.8'
-            python-version: '3.8.10'
-          - python-version-short: '3.9'
-            python-version: '3.9.14'
+        python:
+          - {version-short: '3.8', version: '3.8.10'}
+          - {version-short: '3.9', version: '3.9.14'}
 
     services:
       mongo:
@@ -188,11 +271,11 @@ jobs:
           git submodule foreach 'git fetch --all --tags'
           git submodule foreach 'git tag'
 
-      - name: 'Set up Python (${{ matrix.python-version }})'
+      - name: 'Set up Python (${{ matrix.python.version }})'
         id: python
         uses: actions/setup-python@v5
         with:
-          python-version: '${{ matrix.python-version }}'
+          python-version: '${{ matrix.python.version }}'
 
       - name: Cache and Install APT Dependencies
         uses: ./.github/actions/apt-packages
@@ -201,7 +284,7 @@ jobs:
         uses: ./.github/actions/init-pants
         with:
           # To ignore a bad cache, bump the cache* integer.
-          gha-cache-key: cache0-py${{ matrix.python-version }}
+          gha-cache-key: cache0-py${{ matrix.python.version }}
 
       - name: Pack Tests
         env:
@@ -217,7 +300,7 @@ jobs:
       - name: Upload pants log
         uses: actions/upload-artifact@v4
         with:
-          name: pants-log-py${{ matrix.python-version }}
+          name: pants-log-py${{ matrix.python.version }}-pack-tests
           path: .pants.d/pants.log
         if: always()  # We want the log even on failures.