diff --git a/.github/workflows/coding-standards.yml b/.github/workflows/coding-standards.yml
index 8109118f9b..ad81be3290 100644
--- a/.github/workflows/coding-standards.yml
+++ b/.github/workflows/coding-standards.yml
@@ -32,6 +32,7 @@ on:
       - 'phpcs.xml.dist'
       # Changes to workflow files should always verify all workflows are successful.
       - '.github/workflows/*.yml'
+  workflow_dispatch:
 
 jobs:
   # Runs PHP coding standards checks.
diff --git a/.github/workflows/end-to-end-tests.yml b/.github/workflows/end-to-end-tests.yml
index fb3f281c5e..0a59c51a4c 100644
--- a/.github/workflows/end-to-end-tests.yml
+++ b/.github/workflows/end-to-end-tests.yml
@@ -17,6 +17,7 @@ on:
       - trunk
       - '5.[3-9]'
       - '[6-9].[0-9]'
+  workflow_dispatch:
 
 env:
   LOCAL_DIR: build
diff --git a/.github/workflows/javascript-tests.yml b/.github/workflows/javascript-tests.yml
index a2d4758a36..0bf9f5a461 100644
--- a/.github/workflows/javascript-tests.yml
+++ b/.github/workflows/javascript-tests.yml
@@ -30,6 +30,7 @@ on:
       - 'tests/qunit/**'
       # Changes to workflow files should always verify all workflows are successful.
       - '.github/workflows/*.yml'
+  workflow_dispatch:
 
 jobs:
   # Runs the QUnit tests for WordPress.
diff --git a/.github/workflows/php-compatibility.yml b/.github/workflows/php-compatibility.yml
index 0ca0761297..78b63abccf 100644
--- a/.github/workflows/php-compatibility.yml
+++ b/.github/workflows/php-compatibility.yml
@@ -26,6 +26,7 @@ on:
       - 'phpcompat.xml.dist'
       # Changes to workflow files should always verify all workflows are successful.
       - '.github/workflows/*.yml'
+  workflow_dispatch:
 
 jobs:
 
diff --git a/.github/workflows/phpunit-tests.yml b/.github/workflows/phpunit-tests.yml
index c5b5947785..daf04b146d 100644
--- a/.github/workflows/phpunit-tests.yml
+++ b/.github/workflows/phpunit-tests.yml
@@ -14,6 +14,7 @@ on:
       - master
       - '3.[7-9]'
       - '[4-9].[0-9]'
+  workflow_dispatch:
   # Once weekly On Sundays at 00:00 UTC.
   schedule:
     - cron: '0 0 * * 0'
diff --git a/.github/workflows/test-npm.yml b/.github/workflows/test-npm.yml
index 8a3d9db82e..8362db4c6d 100644
--- a/.github/workflows/test-npm.yml
+++ b/.github/workflows/test-npm.yml
@@ -23,6 +23,7 @@ on:
       - '**.css'
       # Changes to workflow files should always verify all workflows are successful.
       - '.github/workflows/**.yml'
+  workflow_dispatch:
 
 env:
   PUPPETEER_SKIP_CHROMIUM_DOWNLOAD: ${{ true }}
diff --git a/.github/workflows/test-old-branches.yml b/.github/workflows/test-old-branches.yml
new file mode 100644
index 0000000000..76aef76dfd
--- /dev/null
+++ b/.github/workflows/test-old-branches.yml
@@ -0,0 +1,58 @@
+name: Test old branches
+
+on:
+  # Once weekly On Mondays at 00:00 UTC.
+  schedule:
+    - cron: '0 0 1,15 * *'
+
+jobs:
+  dispatch-workflows-for-old-branches:
+    name: ${{ matrix.workflow }} for ${{ matrix.branch }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        workflow: [
+            'coding-standards.yml',
+            'javascript-tests.yml',
+            'phpunit-tests.yml',
+            'test-npm.yml'
+        ]
+        branch: [
+            '5.7', '5.6', '5.5', '5.4', '5.3', '5.2', '5.1', '5.0',
+            '4.9', '4.8', '4.7', '4.6', '4.5', '4.4', '4.3', '4.2', '4.1', '4.0',
+            '3.9', '3.8', '3.7'
+        ]
+        include:
+          # PHP Compatibility testing was introduced in 5.5.
+          - branch: '5.7'
+            workflow: 'php-compatibility.yml'
+          - branch: '5.6'
+            workflow: 'php-compatibility.yml'
+          - branch: '5.5'
+            workflow: 'php-compatibility.yml'
+
+          # End to End testing was introduced in 5.3 but later removed as there were no meaningful assertions.
+          # Only the officially supported major branch runs E2E tests so that more assertions can be added, and the
+          # workflow does not continue to run needlessly on old branches.
+          - branch: '5.7'
+            workflow: 'end-to-end-tests.yml'
+        exclude:
+          # Coding standards and JavaScript testing did not take place in 3.7.
+          - branch: '3.7'
+            workflow: 'coding-standards.yml'
+          - branch: '3.7'
+            workflow: 'javascript-tests.yml'
+
+    steps:
+      - name: Dispatch workflow run
+        uses: actions/github-script@47f7cf65b5ced0830a325f705cad64f2f58dddf7 # v3.1.0
+        with:
+          github-token: ${{ secrets.GHA_OLD_BRANCH_DISPATCH }}
+          script: |
+            github.actions.createWorkflowDispatch({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              workflow_id: '${{ matrix.workflow }}',
+              ref: '${{ matrix.branch }}'
+            });