diff --git a/etc/ci/buildbot_steps.yml b/etc/ci/buildbot_steps.yml
index b80ed719e1f8..fa0ba8a2226b 100644
--- a/etc/ci/buildbot_steps.yml
+++ b/etc/ci/buildbot_steps.yml
@@ -73,6 +73,9 @@ mac-nightly:
   - env PKG_CONFIG_PATH=/usr/local/opt/zlib/lib/pkgconfig ./mach build --release
   - ./mach package --release
   - ./mach upload-nightly mac
+  - ./etc/ci/update-wpt-checkout fetch-and-update-expectations
+  - ./etc/ci/update-wpt-checkout open-pr
+  - ./etc/ci/update-wpt-checkout cleanup
 
 linux-rel-intermittent:
   - ./mach clean-nightlies --keep 3 --force
diff --git a/etc/ci/update-wpt-checkout b/etc/ci/update-wpt-checkout
new file mode 100755
index 000000000000..6203d4641917
--- /dev/null
+++ b/etc/ci/update-wpt-checkout
@@ -0,0 +1,186 @@
+#!/usr/bin/env bash
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+REMOTE_NAME=sync-fork
+LOG_FILE=test-wpt.log
+CURRENT_DATE=$(date +"%d-%m-%Y")
+BRANCH_NAME="wpt_update_${CURRENT_DATE}"
+
+export GIT_AUTHOR_NAME="WPT Sync Bot"
+export GIT_AUTHOR_EMAIL="josh+wptsync@joshmatthews.net"
+
+# Retrieve the HEAD commit and extract its hash
+function latest_git_commit() {
+    git log -1 --oneline | cut -f 1 -d ' '
+}
+
+# Create a new branch for this sync, pull down all changes from the upstream
+# web-platform-tests repository, and commit the changes.
+function unsafe_pull_from_upstream() {
+    git checkout -b "${1}" || return 1
+
+    OLD_COMMIT=$(latest_git_commit)
+
+    # Fetch all changes from upstream WPT and automatically transpose them
+    # into a single servo commit.
+    ./mach update-wpt --sync --no-upstream --patch || return 2
+
+    # If there was no new commit created, there are no changes that need syncing.
+    # Skip the remaining steps.
+    if [[ "$(latest_git_commit)" == "${OLD_COMMIT}" ]]; then
+        return 255
+    fi
+
+    # Update the manifest to include the new changes.
+    ./mach update-manifest || return 3
+
+    # Amend the existing commit with the new changes from updating the manifest.
+    git commit -a --amend --no-edit || return 4
+}
+
+# Remove all local traces of this sync operation.
+function cleanup() {
+    git remote rm "${REMOTE_NAME}" || true
+    git reset --hard || true
+    git checkout master || true
+    git branch -D "${BRANCH_NAME}" || true
+    ./mach update-wpt --abort || true
+}
+
+# Build Servo and run the full WPT testsuite, saving the results to a log file.
+function unsafe_run_tests() {
+    # Run the full testsuite and record the new test results.
+    ./mach test-wpt --release --processes 24 --log-raw "${1}" \
+           --always-succeed || return 1
+}
+
+# Using an existing log file, update the expected test results and amend the
+# last commit with the new results.
+function unsafe_update_metadata() {
+    ./mach update-wpt "${1}" || return 1
+    # Ignore any metadata changes to files that weren't modified by this sync.
+    git checkout -- tests/wpt/mozilla/meta || return 2
+    # Ensure any new directories or ini files are included in these changes.
+    git add tests/wpt/metadata || return 3
+    # Merge all changes with the existing commit.
+    git commit -a --amend --no-edit || return 4
+}
+
+# Push the branch to a remote branch, then open a PR for the branch
+# against servo/servo.
+function unsafe_open_pull_request() {
+    WPT_SYNC_USER=servo-wpt-sync
+
+    # If the branch doesn't exist, we'll silently exit. This deals with the
+    # case where an earlier step either failed or discovered that syncing
+    # is unnecessary.
+    git checkout "${BRANCH_NAME}" || return 0
+
+    if [[ -z "${WPT_SYNC_TOKEN+set}" ]]; then
+        echo "Github auth token missing from WPT_SYNC_TOKEN."
+        return 1
+    fi
+
+    # Push the changes to a remote branch owned by the bot.
+    AUTH="${WPT_SYNC_USER}:${WPT_SYNC_TOKEN}"
+    UPSTREAM="https://${AUTH}@github.com/${WPT_SYNC_USER}/servo.git"
+    git remote add "${REMOTE_NAME}" "${UPSTREAM}" || return 2
+    git push -f "${REMOTE_NAME}" "${BRANCH_NAME}" || return 3
+
+    # Prepare the pull request metadata.
+    BODY="Automated downstream sync of changes from upstream as of "
+    BODY+="${CURRENT_DATE}.\n"
+    BODY+="[no-wpt-sync]"
+    cat <<EOF >prdata.json || return 4
+{
+  "title": "Sync WPT with upstream (${CURRENT_DATE})",
+  "head": "${WPT_SYNC_USER}:${BRANCH_NAME}",
+  "base": "master",
+  "body": "${BODY}",
+  "maintainer_can_modify": true
+}
+EOF
+
+    # Open a pull request using the new branch.
+    curl -H "Authorization: token ${WPT_SYNC_TOKEN}" \
+         -H "Content-Type: application/json" \
+         --data @prdata.json \
+         https://api.github.com/repos/servo/servo/pulls || return 4
+}
+
+function pull_from_upstream() {
+    unsafe_pull_from_upstream "${1}" || { code="${?}"; cleanup; return "${code}"; }
+}
+
+function run_tests() {
+    unsafe_run_tests "${1}" || { code="${?}"; cleanup; return "${code}"; }
+}
+
+function update_metadata() {
+    unsafe_update_metadata "${1}" || { code="${?}"; cleanup; return "${code}"; }
+}
+
+function open_pull_request() {
+    unsafe_open_pull_request || { code="${?}"; cleanup; return "${code}"; }
+}
+
+SCRIPT_NAME="${0}"
+
+function update_test_results() {
+    run_tests "${LOG_FILE}"
+    update_metadata "${LOG_FILE}"
+}
+
+function fetch_upstream_changes() {
+    pull_from_upstream "${BRANCH_NAME}"
+}
+
+function usage() {
+    echo "usage: ${SCRIPT_NAME} [cmd]"
+    echo "  commands:"
+    echo "  - fetch-upstream-changes: create a branch with the latest changes from upstream"
+    echo "  - update-test-results: run the tests, update the expected test results, and commit the changes"
+    echo "  - fetch-and-update-expectations: combines fetch-upstream-changes and update-test-results"
+    echo "  - open-pr: open a pull request with the latest changes"
+    echo "  - cleanup: cleanup all traces of an in-progress sync and checkout the master branch"
+    exit 1
+}
+
+function main() {
+    if [[ "${1}" == "fetch-upstream-changes" ]] || [[ "${1}" == "fetch-and-update-expectations" ]]; then
+        code=""
+        fetch_upstream_changes || code="${?}"
+        if [[ "${code}" == "255" ]]; then
+            echo "No changes to sync."
+            return 0
+        fi
+    fi
+
+    if [[ "${1}" == "update-test-results" ]] || [[ "${1}" == "fetch-and-update-expectations" ]]; then
+        update_test_results
+
+    elif [[ "${1}" == "open-pr" ]]; then
+        open_pull_request
+
+    elif [[ "${1}" == "cleanup" ]]; then
+        cleanup
+
+    else
+        usage
+    fi
+}
+
+if [[ "$#" != 1 ]]; then
+    usage
+fi
+
+# Ensure we clean up after ourselves if this script is interrupted.
+trap 'cleanup' SIGINT SIGTERM
+main "${1}"