diff --git a/.github/workflows/update-wasm-tests.yml b/.github/workflows/update-wasm-tests.yml
new file mode 100644
index 00000000000000..42e4cb9ed8f231
--- /dev/null
+++ b/.github/workflows/update-wasm-tests.yml
@@ -0,0 +1,65 @@
+name: Update WASM tests
+
+on:
+  # Trigger at every Sunday UTC noon, or manually.
+  schedule:
+    - cron: 0 12 * * 0
+  workflow_dispatch:
+
+jobs:
+  build-wpt:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout WPT repo
+        uses: actions/checkout@v4
+        with:
+          path: main
+      - name: Checkout WASM repo
+        uses: actions/checkout@v4
+        with:
+          repository: WebAssembly/spec
+          path: wasm-spec
+      - name: Setup OCaml
+        uses: ocaml/setup-ocaml@v3
+        with:
+          ocaml-compiler: 4.14.x
+      - name: Setup OCaml tools
+        run: opam install --yes ocamlfind.1.9.5 js_of_ocaml.4.0.0 js_of_ocaml-ppx.4.0.0
+      - name: Build interpreter
+        run: cd wasm-spec/interpreter && opam exec make
+      - name: Convert WAST tests to WPT
+        run: wasm-spec/test/build.py --dont-recompile --html wasm-spec/out/
+      - name: Copy WASM tests to WPT
+        # Replace wasm/core entirely and fix up testharness paths.
+        run: |
+          rm -rf main/wasm/core
+          cp -r wasm-spec/out/ main/wasm/core/
+          find main/wasm/core/ -type f -name '*.html' -exec sed -i 's/\.\/js\/harness\/testharness/\/resources\/testharness/' {} \;
+      - name: Commit changes
+        id: commit
+        continue-on-error: true
+        run: |
+          cd main
+          export BRANCH_NAME="$BRANCH_PREFIX-$(date +'%Y%m%d%H%M%S')"
+          echo "BRANCH_NAME=$BRANCH_NAME" >> $GITHUB_ENV
+          git config user.name "$GIT_AUTHOR_NAME"
+          git config user.email "$GIT_AUTHOR_EMAIL"
+          git checkout -b $BRANCH_NAME
+          git add wasm/core/
+          git commit -m "$COMMIT_TITLE"
+        env:
+          GIT_AUTHOR_NAME: "wpt-pr-bot"
+          GIT_AUTHOR_EMAIL: "wpt-pr-bot@users.noreply.github.com"
+          BRANCH_PREFIX: "wasm-update"
+          COMMIT_TITLE: "Update WASM tests"
+      - name: Create PR
+        # Check outcome for success as continue-on-error will mask failure.
+        if: ${{ steps.commit.outcome == 'success' }}
+        run: |
+          cd main
+          git push --set-upstream origin $BRANCH_NAME
+          gh pr create --title "$COMMIT_TITLE" --body "$PR_BODY" --reviewer past
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          COMMIT_TITLE: "Update WASM tests"
+          PR_BODY: "Scheduled weekly update auto-generated by the '${{ github.workflow }}' workflow."