diff --git a/Makefile b/Makefile
index c4c9f05..020d753 100644
--- a/Makefile
+++ b/Makefile
@@ -2,6 +2,7 @@ ACTIONS := \
 	docker \
 	node \
 	git/create_tag \
+	git/promotion-gate \
 	helm/diff \
 	helm/template \
 	helm/upgrade \
diff --git a/README.md b/README.md
index b3f8b1e..b4aa160 100644
--- a/README.md
+++ b/README.md
@@ -15,6 +15,7 @@ Reusable composite actions for Gitea CI/CD pipelines.
 | Action | Description |
 |---|---|
 | [git/create_tag](git/create_tag/README.md) | Create and push a git tag in the current repository |
+| [git/promotion-gate](git/promotion-gate/README.md) | Enforce which source branches may merge into which target branches |
 
 ### Helm
 
diff --git a/git/promotion-gate/README.md b/git/promotion-gate/README.md
new file mode 100644
index 0000000..be86dba
--- /dev/null
+++ b/git/promotion-gate/README.md
@@ -0,0 +1,21 @@
+# Promotion Gate
+
+<!-- action-docs-description source="action.yml" -->
+## Description
+
+Enforce which source branches may merge into which target branches
+<!-- action-docs-description source="action.yml" -->
+
+<!-- action-docs-inputs source="action.yml" -->
+## Inputs
+
+| name | description | required | default |
+| --- | --- | --- | --- |
+| `rules` | <p>One rule per line: "target:allowed1,allowed2,…". Targets not listed are unrestricted. Allowed entries may use a trailing glob, e.g. <code>hotfix-*</code>. Leave empty (default) to skip entirely.</p> | `false` | `""` |
+<!-- action-docs-inputs source="action.yml" -->
+
+<!-- action-docs-runs source="action.yml" -->
+## Runs
+
+This action is a `composite` action.
+<!-- action-docs-runs source="action.yml" -->
diff --git a/git/promotion-gate/action.yml b/git/promotion-gate/action.yml
new file mode 100644
index 0000000..284e760
--- /dev/null
+++ b/git/promotion-gate/action.yml
@@ -0,0 +1,75 @@
+name: Promotion Gate
+description: Enforce which source branches may merge into which target branches
+inputs:
+  rules:
+    description: |
+      One rule per line: "target:allowed1,allowed2,...". Targets not
+      listed are unrestricted. Allowed entries may use a trailing glob,
+      e.g. `hotfix-*`. Leave empty (default) to skip entirely.
+    default: ""
+
+runs:
+  using: composite
+  steps:
+    - name: Check merge source is allowed for target branch
+      shell: sh
+      env:
+        BASE: ${{ gitea.event.pull_request.base.ref }}
+        HEAD: ${{ gitea.event.pull_request.head.ref }}
+        RULES: ${{ inputs.rules }}
+      run: |
+        if [ -z "$RULES" ]; then
+          echo "No promotion rules configured — skipping."
+          exit 0
+        fi
+
+        rc=0
+        found=0
+
+        oldIFS=$IFS
+        IFS='
+        '
+        set -f
+        set -- $RULES
+        set +f
+        IFS=$oldIFS
+
+        for line in "$@"; do
+          if [ -z "$line" ]; then
+            continue
+          fi
+          target=${line%%:*}
+          allowed=${line#*:}
+          if [ "$target" = "$line" ]; then
+            continue
+          fi
+          if [ "$BASE" = "$target" ]; then
+            found=1
+            matched=0
+            innerIFS=$IFS
+            IFS=','
+            for pat in $allowed; do
+              IFS=$innerIFS
+              case "$HEAD" in
+                $pat)
+                  matched=1
+                  ;;
+              esac
+              IFS=','
+            done
+            IFS=$innerIFS
+
+            if [ "$matched" -eq 1 ]; then
+              echo "Allowed: '$HEAD' -> '$BASE' (matches: $allowed)"
+            else
+              echo "::error::$BASE only accepts merges from: $allowed — got '$HEAD'"
+              rc=1
+            fi
+          fi
+        done
+
+        if [ "$found" -eq 0 ]; then
+          echo "No promotion-source restriction configured for base '$BASE'"
+        fi
+
+        exit $rc