diff --git a/.github/workflows/update_splink4_merge_branch.yml b/.github/workflows/update_splink4_merge_branch.yml
new file mode 100644
index 0000000000..c855f8c29f
--- /dev/null
+++ b/.github/workflows/update_splink4_merge_branch.yml
@@ -0,0 +1,36 @@
+name: update_splink4_merge_branch
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  update-merge-branch:
+    runs-on: ubuntu-20.04
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v3
+        with:
+          ref: master
+          fetch-depth: 0
+
+      - name: Check if branch exists already and create if not
+        run: |
+            git fetch
+            if git ls-remote --exit-code --heads origin merge/splink_3_to_4; then
+              echo "Branch merge/splink_3_to_4 exists"
+            else
+              git switch -c merge/splink_3_to_4
+              git push -u origin merge/splink_3_to_4
+            fi
+
+      - name: Update to-merge branch
+        run: |
+            git fetch
+            git switch merge/splink_3_to_4
+            git pull --ff-only
+            git config --global user.email "41898282+github-actions[bot]@users.noreply.github.com"
+            git config --global user.name "github-actions[bot]"
+            git merge origin/master
+            git push origin merge/splink_3_to_4