diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..9395e79
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,67 @@
+---
+name: CI
+
+on:
+  pull_request:
+    branches: [master]
+    types: [opened, synchronize, reopened]
+  push:
+    branches: [master]
+  workflow_dispatch:
+
+concurrency:
+  group: "${{ github.workflow }}-${{ github.ref }}"
+  cancel-in-progress: true
+
+jobs:
+  action:
+    environment:
+      ${{ github.event_name == 'pull_request' &&
+      github.event.pull_request.head.repo.full_name != github.repository &&
+      'external' || 'internal' }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Release
+        id: setup-release
+        uses: LizardByte/setup-release-action@fix!-updates  # todo: change to latest
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}  # can use GITHUB_TOKEN for read-only access
+
+      - name: Set action variables
+        id: vars
+        run: |
+          if [ "${{ github.event_name }}" == "pull_request" ]; then
+            changelog_branch=pr-changelogs
+            changelog_file=PR-${{ github.event.pull_request.number }}-CHANGELOG.md
+          else
+            changelog_branch=changelog
+            changelog_file=CHANGELOG.md
+          fi
+
+          # set outputs
+          echo "changelog_branch=$changelog_branch" >> $GITHUB_OUTPUT
+          echo "changelog_file=$changelog_file" >> $GITHUB_OUTPUT
+
+      - name: Run Action
+        id: action
+        uses: ./
+        with:
+          changelogBranch: ${{ steps.vars.outputs.changelog_branch }}
+          changelogFile: ${{ steps.vars.outputs.changelog_file }}
+          token: ${{ secrets.GH_BOT_TOKEN }}
+
+      - name: Create/Update GitHub Release
+        if: ${{ steps.setup-release.outputs.publish_release == 'true' }}
+        uses: LizardByte/create-release-action@fix!-updates  # todo: change to latest
+        with:
+          allowUpdates: false
+          artifacts: ""
+          discussionCategory: announcements
+          generateReleaseNotes: true
+          name: ${{ steps.setup-release.outputs.release_tag }}
+          prerelease: true
+          tag: ${{ steps.setup-release.outputs.release_tag }}
+          token: ${{ secrets.GH_BOT_TOKEN }}
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..225ce7e
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+# ignore jetbrains files
+.idea/
diff --git a/README.md b/README.md
index fd3e658..a3cc366 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,35 @@
-# template-base
-Base repository template for LizardByte.
+# update-changelog-action
+[![GitHub Workflow Status (CI)](https://img.shields.io/github/actions/workflow/status/lizardbyte/update-changelog-action/ci.yml.svg?branch=master&label=CI%20build&logo=github&style=for-the-badge)](https://github.com/LizardByte/update-changelog-action/actions/workflows/ci.yml?query=branch%3Amaster)
+
+A reusable action to update a changelog, based on the contents of the GitHub releases.
+
+## Basic Usage
+
+See [action.yml](action.yml)
+
+```yaml
+steps:
+  - name: Update Changelog
+    uses: LizardByte/update-changelog-action@master
+    with:
+      token: ${{ secrets.GITHUB_TOKEN }}
+```
+
+## Inputs
+
+| Name                   | Description                            | Default         | Required |
+|------------------------|----------------------------------------|-----------------|----------|
+| changelogBranch        | The branch to store the changelog in.  | `changelog`     | `false`  |
+| changelogFile          | The file to store the changelog in.    | `CHANGELOG.md`  | `false`  |
+| token                  | GitHub Token.                          |                 | `true`   |
+
+## Outputs
+
+| Name      | Description                              |
+|-----------|------------------------------------------|
+| changelog | The contents of the generated changelog. |
+
+## See Also
+
+This action is meant to be used in conjunction with
+[LizardByte/setup-release-action](https://github.com/LizardByte/setup-release-action).
diff --git a/action.yml b/action.yml
new file mode 100644
index 0000000..e144025
--- /dev/null
+++ b/action.yml
@@ -0,0 +1,163 @@
+---
+name: "Update changelog"
+description: "A reusable action to automatically update a changelog based on GitHub releases."
+author: "LizardByte"
+inputs:
+  changelogBranch:
+    description: 'The branch to store the changelog in.'
+    required: false
+    default: 'changelog'
+  changelogFile:
+    description: 'The file to store the changelog in.'
+    required: false
+    default: 'CHANGELOG.md'
+  token:
+    description: 'Github Token.'
+    required: true
+
+runs:
+  using: "composite"
+  steps:
+    - name: Create Changelog
+      env:
+        changelog_branch: ${{ inputs.changelogBranch }}
+        changelog_file: ${{ inputs.changelogFile }}
+      uses: actions/github-script@v7
+      with:
+        github-token: ${{ inputs.token }}
+        script: |
+          // get inputs
+          const changelogBranch = process.env.changelog_branch
+          const changelogFile = process.env.changelog_file
+
+          // get all releases and sort by date created, page if required
+          let releases = []
+          let page = 1
+          let per_page = 100
+          let total = 0
+          do {
+              const response = await github.rest.repos.listReleases({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  per_page: per_page,
+                  page: page
+              })
+              releases = releases.concat(response.data)
+              total = response.data.length
+              page++
+          } while (total == per_page)
+          // sort releases by date created
+          releases.sort((a, b) => {
+              return new Date(a.created_at) - new Date(b.created_at)
+          })
+
+          // create a CHANGELOG.md and initialize it
+          let changelog = '<!-- # Changelog -->\n\n'  // commenting out due to how sphinx renders this
+          changelog += 'All notable changes to this project will be documented in this file.\n\n'
+          changelog += 'The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),\n'
+          changelog += 'and this project adheres to [Calendar Versioning](https://calver.org/).\n\n'
+          changelog += 'This changelog was automatically generated by the\n'
+          changelog += '[create-release-action](https://github.com/LizardByte/create-release-action).\n\n'
+
+          // loop through each release
+          releases = releases.reverse()
+          for (const release of releases) {
+              // add release to changelog
+              let created_date = new Date(release.created_at)
+              let year = created_date.getFullYear()
+              let month = (created_date.getMonth() + 1).toString().padStart(2, '0')
+              let day = created_date.getDate().toString().padStart(2, '0')
+              let date = `${year}-${month}-${day}`
+
+              // replace lines such as `## Any Text\n` with `**Any Text**\n`
+              // let release_body = release.body.replace(/## (.*)\n/g, '**$1**\n')
+              // replace lines such as `## Any Text\n` with `### Any Text\n`
+              let release_body = release.body.replace(/## (.*)\n/g, '### $1\n')
+              changelog += `## [${release.tag_name}] - ${date}\n\n${release_body}\n\n`
+          }
+
+          // add urls to end of changelog
+          for (const release of releases) {
+              // add release url to changelog
+              changelog += `[${release.tag_name}]: ${release.html_url}\n`
+          }
+
+          try {
+              // Directly create a tree with CHANGELOG.md in it
+              const blob = await github.rest.git.createBlob({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  content: changelog,
+                  encoding: 'utf-8'
+              })
+
+              const tree = await github.rest.git.createTree({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  tree: [{
+                      path: changelogFile,
+                      mode: '100644',
+                      type: 'blob',
+                      sha: blob.data.sha
+                  }]
+              })
+
+              const commit = await github.rest.git.createCommit({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  message: `chore: create ${changelogFile}`,
+                  tree: tree.data.sha,
+                  parents: [] // Empty parents array for a truly orphaned commit
+              })
+
+              await github.rest.git.createRef({
+                  owner: context.repo.owner,
+                  repo: context.repo.repo,
+                  ref: `refs/heads/${changelogBranch}`,
+                  sha: commit.data.sha
+              })
+          } catch (e) {
+              if (e.status === 422 && e.message.includes("Reference already exists")) {
+                  let sha = null; // Initialize the sha to null by default
+
+                  // Branch already exists, try to fetch the SHA of the specified changelogFile
+                  try {
+                      const fileData = await github.rest.repos.getContent({
+                          owner: context.repo.owner,
+                          repo: context.repo.repo,
+                          path: changelogFile,
+                          ref: changelogBranch
+                      });
+
+                      sha = fileData.data.sha; // Update the sha if the file exists
+                  } catch (getFileError) {
+                      if (getFileError.status !== 404) {
+                          // If the error is not a 'not found' error, set the action as failed
+                          core.setFailed(`Failed to fetch the file: ${getFileError.message}`);
+                          return;
+                      }
+                      // If the error is 'not found' error, we'll continue with sha as null, resulting in file creation
+                  }
+
+                  try {
+                      // Create or Update the file using the same call
+                      await github.rest.repos.createOrUpdateFileContents({
+                          owner: context.repo.owner,
+                          repo: context.repo.repo,
+                          path: changelogFile,
+                          message: sha ? `chore: update ${changelogFile}` : `chore: create ${changelogFile}`,
+                          content: Buffer.from(changelog).toString('base64'),
+                          sha: sha, // if sha is null, it'll create a new file
+                          branch: changelogBranch
+                      });
+                  } catch (updateError) {
+                      core.setFailed(`Failed to create or update the file: ${updateError.message}`);
+                  }
+              } else {
+                  // Some other error occurred
+                  core.setFailed(`Action failed with error: ${e.message}`);
+              }
+          }
+
+          // Set GitHub action output
+          core.setOutput('changelog', changelog);