diff --git a/.github/workflows/build_packages.yml b/.github/workflows/build_packages.yml
index 7b79225ce..ed469a0b2 100644
--- a/.github/workflows/build_packages.yml
+++ b/.github/workflows/build_packages.yml
@@ -14,3 +14,6 @@ jobs:
       run: source tools/ci.sh && ci_build_packages_check_manifest
     - name: Compile package index
       run: source tools/ci.sh && ci_build_packages_compile_index
+    - name: Publish packages for branch
+      if: vars.MICROPY_PUBLISH_MIP_INDEX && github.event_name == 'push' && ! github.event.deleted
+      run: source tools/ci.sh && ci_push_package_index
diff --git a/.github/workflows/cleanup_published_packages.yml b/.github/workflows/cleanup_published_packages.yml
new file mode 100644
index 000000000..c6a33cece
--- /dev/null
+++ b/.github/workflows/cleanup_published_packages.yml
@@ -0,0 +1,12 @@
+name: Cleanup published packages
+
+on: delete
+
+jobs:
+  cleanup:
+    runs-on: ubuntu-latest
+    if: vars.MICROPY_PUBLISH_MIP_INDEX
+    steps:
+    - uses: actions/checkout@v2
+    - name: Clean up published files
+      run: source tools/ci.sh && ci_cleanup_package_index ${{ github.event.ref }}
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 715477171..804a26bef 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -69,3 +69,49 @@ There are some specific conventions and guidelines for micropython-lib:
 
 * When porting an existing third-party package, please ensure that the source
   license is compatible.
+
+* To make it easier for others to install packages directly from your PR before
+  it is merged, consider opting-in to automatic package publishing (see
+  [Publishing packages from forks](#publishing-packages-from-forks)). If you do
+  this, consider quoting the [commands to install
+  packages](README.md#installing-packages-from-forks) in your Pull Request
+  description.
+
+### Publishing packages from forks
+
+You can easily publish the packages from your micropython-lib
+[fork](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/about-forks)
+by opting in to a system based on [GitHub
+Actions](https://docs.github.com/en/actions) and [GitHub
+Pages](https://docs.github.com/en/pages):
+
+1. Open your fork's repository in the GitHub web interface.
+2. Navigate to "Settings" -> "Secrets and variables" -> "Actions" -> "Variables".
+3. Click "New repository variable"
+4. Create a variable named `MICROPY_PUBLISH_MIP_INDEX` with value `true` (or any
+   "truthy" value).
+5. The settings for GitHub Actions and GitHub Pages features should not need to
+   be changed from the repository defaults, unless you've explicitly disabled
+   them.
+
+The next time you push commits to a branch in your fork, GitHub Actions will run
+an additional step in the "Build All Packages" workflow named "Publish Packages
+for branch".
+
+Anyone can then install these packages as described under [Installing packages
+from forks](README.md#installing-packages-from-forks). The exact commands are also
+quoted in the GitHub Actions log for the "Publish Packages for branch" step.
+
+#### Opting Back Out
+
+To opt-out again, delete the `MICROPY_PUBLISH_MIP_INDEX` variable and
+(optionally) delete the `gh-pages` branch from your fork.
+
+*Note*: While enabled, all micropython-lib packages will be published each time
+a change is pushed to any branch in your fork. A commit is added to the
+`gh-pages` branch each time. In a busy repository, the `gh-pages` branch may
+become quite large. The actual `.git` directory size on disk should still be
+quite small, as most of the content will be duplicated. If you're worried that
+the `gh-pages` branch has become too large then you can always delete this
+branch from GitHub. GitHub Actions will create a new `gh-pages` branch the next
+time you push a change.
diff --git a/README.md b/README.md
index c47c0acf9..73417b965 100644
--- a/README.md
+++ b/README.md
@@ -84,6 +84,37 @@ Note that unlike the other three approaches based on `mip` or `manifest.py`,
 you will need to manually resolve dependencies. You can inspect the relevant
 `manifest.py` file to view the list of dependencies for a given package.
 
+## Installing packages from forks
+
+It is possible to use the `mpremote mip install` or `mip.install()` methods to
+install packages built from a
+[fork](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/about-forks)
+of micropython-lib, if the fork's owner has opted in.
+
+This can be useful to install packages from a pending Pull Request, for example.
+
+First, the owner of the fork must opt-in as described under
+[Publishing packages from forks](CONTRIBUTING.md#publishing-packages-from-forks).
+
+After this has happened, each time someone pushes to a branch in that fork then
+GitHub Actions will automatically publish the packages to a GitHub Pages site.
+
+To install these packages, use commands such as:
+
+```bash
+$ mpremote connect /dev/ttyUSB0 mip install --index https://USERNAME.github.io/micropython-lib/mip/BRANCH_NAME PACKAGE_NAME
+```
+
+Or from a networked device:
+
+```py
+import mip
+mip.install(PACKAGE_NAME, index="https://USERNAME.github.io/micropython-lib/mip/BRANCH_NAME")
+```
+
+(Where `USERNAME`, `BRANCH_NAME` and `PACKAGE_NAME` are replaced with the owner
+of the fork, the branch the packages were built from, and the package name.)
+
 ## Contributing
 
 We use [GitHub Discussions](https://github.com/micropython/micropython/discussions)
diff --git a/tools/ci.sh b/tools/ci.sh
index 75c8791d5..548680682 100755
--- a/tools/ci.sh
+++ b/tools/ci.sh
@@ -1,5 +1,9 @@
 #!/bin/bash
 
+########################################################################################
+# common "constants"
+PACKAGE_INDEX_PATH=/tmp/micropython-lib-deploy
+
 ########################################################################################
 # code formatting
 
@@ -38,5 +42,104 @@ function ci_build_packages_check_manifest {
 }
 
 function ci_build_packages_compile_index {
-    python3 tools/build.py --micropython /tmp/micropython --output /tmp/micropython-lib-deploy
+    python3 tools/build.py --micropython /tmp/micropython --output $PACKAGE_INDEX_PATH
+}
+
+function ci_push_package_index {
+    set -euo pipefail
+
+    # Note: This feature is opt-in, so this function is only run by GitHub
+    # Actions if the MICROPY_PUBLISH_MIP_INDEX repository variable is set to a
+    # "truthy" value in the "Secrets and variables" -> "Actions"
+    # -> "Variables" setting of the GitHub repo.
+
+    PAGES_PATH=/tmp/gh-pages
+
+    if git fetch --depth=1 origin gh-pages; then
+        git worktree add ${PAGES_PATH} gh-pages
+        cd ${PAGES_PATH}
+        NEW_BRANCH=0
+    else
+        echo "Creating gh-pages branch for $GITHUB_REPOSITORY..."
+        git worktree add --force ${PAGES_PATH} HEAD
+        cd ${PAGES_PATH}
+        git switch --orphan gh-pages
+        NEW_BRANCH=1
+    fi
+
+    DEST_PATH=${PAGES_PATH}/mip/${GITHUB_REF_NAME}
+    if [ -d ${DEST_PATH} ]; then
+        git rm -r ${DEST_PATH}
+    fi
+    mkdir -p ${DEST_PATH}
+    cd ${DEST_PATH}
+
+    cp -r ${PACKAGE_INDEX_PATH}/* .
+
+    git add .
+    git_bot_commit "Add CI built packages from commit ${GITHUB_SHA} of ${GITHUB_REF_NAME}"
+
+    if [ "$NEW_BRANCH" -eq 0 ]; then
+        # A small race condition exists here if another CI job pushes to
+        # gh-pages at the same time, but this narrows the race to the time
+        # between these two commands.
+        git pull --rebase origin gh-pages
+    fi
+    git push origin gh-pages
+
+    INDEX_URL="https://${GITHUB_REPOSITORY_OWNER}.github.io/$(echo ${GITHUB_REPOSITORY} | cut -d'/' -f2-)/mip/${GITHUB_REF_NAME}"
+
+    echo ""
+    echo "--------------------------------------------------"
+    echo "Uploaded package files to GitHub Pages."
+    echo ""
+    echo "Unless GitHub Pages is disabled on this repo, these files can be installed remotely with:"
+    echo ""
+    echo "mpremote mip install --index ${INDEX_URL} PACKAGE_NAME"
+    echo ""
+    echo "or on the device as:"
+    echo ""
+    echo "import mip"
+    echo "mip.install(PACKAGE_NAME, index=\"${INDEX_URL}\")"
+}
+
+function ci_cleanup_package_index()
+{
+    if ! git fetch --depth=1 origin gh-pages; then
+        exit 0
+    fi
+
+    # Argument $1 is github.event.ref, passed in from workflow file.
+    #
+    # this value seems to be a REF_NAME, without heads/ or tags/ prefix. (Can't
+    # use GITHUB_REF_NAME, this evaluates to the default branch.)
+    DELETED_REF="$1"
+
+    if [ -z "$DELETED_REF" ]; then
+        echo "Bad DELETE_REF $DELETED_REF"
+        exit 1  # Internal error with ref format, better than removing all mip/ directory in a commit
+    fi
+
+    # We need Actions to check out default branch and run tools/ci.sh, but then
+    # we switch branches
+    git switch gh-pages
+
+    echo "Removing any published packages for ${DELETED_REF}..."
+    if [ -d mip/${DELETED_REF} ]; then
+        git rm -r mip/${DELETED_REF}
+        git_bot_commit "Remove CI built packages from deleted ${DELETED_REF}"
+        git pull --rebase origin gh-pages
+        git push origin gh-pages
+    else
+        echo "Nothing to remove."
+    fi
+}
+
+# Make a git commit with bot authorship
+# Argument $1 is the commit message
+function git_bot_commit {
+    # Ref https://github.com/actions/checkout/discussions/479
+    git config user.name 'github-actions[bot]'
+    git config user.email 'github-actions[bot]@users.noreply.github.com'
+    git commit -m "$1"
 }