diff --git a/README.md b/README.md
index 1a1060a..fd896a1 100644
--- a/README.md
+++ b/README.md
@@ -15,7 +15,7 @@ Runs [Prettier](https://prettier.io) on your changed files.
 Supported source control managers:
 
 * Git
-* _Add more_
+* Mercurial
 
 ## Install
 
@@ -54,6 +54,8 @@ With `npm`:
 
 You can run `pretty-quick` as a pre-commit hook using [`husky`](https://github.com/typicode/husky).
 
+> For Mercurial have a look at [`husky-hg`](https://github.com/TobiasTimm/husky-hg)
+
 ```shellstream
 yarn add --dev husky
 ```
diff --git a/package.json b/package.json
index 4f0dd1c..e8a247d 100644
--- a/package.json
+++ b/package.json
@@ -7,6 +7,17 @@
   "main": "./dist",
   "bin": "./bin/pretty-quick.js",
   "license": "MIT",
+  "keywords": [
+    "git",
+    "mercurial",
+    "hg",
+    "prettier",
+    "pretty-quick",
+    "formatting",
+    "code",
+    "vcs",
+    "precommit"
+  ],
   "files": [
     "bin",
     "dist",
diff --git a/src/__tests__/scm-hg.test.js b/src/__tests__/scm-hg.test.js
new file mode 100644
index 0000000..d01e3dc
--- /dev/null
+++ b/src/__tests__/scm-hg.test.js
@@ -0,0 +1,137 @@
+import mock from 'mock-fs';
+import execa from 'execa';
+import fs from 'fs';
+
+import prettyQuick from '..';
+
+jest.mock('execa');
+
+afterEach(() => {
+  mock.restore();
+  jest.clearAllMocks();
+});
+
+const mockHgFs = () => {
+  mock({
+    '/.hg': {},
+    '/foo.js': 'foo()',
+    '/bar.md': '# foo',
+  });
+  execa.sync.mockImplementation((command, args) => {
+    if (command !== 'hg') {
+      throw new Error(`unexpected command: ${command}`);
+    }
+    switch (args[0]) {
+      case 'status':
+        return { stdout: './foo.js\n' + './bar.md\n' };
+      case 'diff':
+        return { stdout: './foo.js\n' + './bar.md\n' };
+      case 'add':
+        return { stdout: '' };
+      case 'log':
+        return { stdout: '' };
+      default:
+        throw new Error(`unexpected arg0: ${args[0]}`);
+    }
+  });
+};
+
+describe('with hg', () => {
+  test('calls `hg debugancestor`', () => {
+    mock({
+      '/.hg': {},
+    });
+
+    prettyQuick('root');
+
+    expect(execa.sync).toHaveBeenCalledWith(
+      'hg',
+      ['debugancestor', 'tip', 'default'],
+      { cwd: '/' }
+    );
+  });
+
+  test('calls `hg debugancestor` with root hg directory', () => {
+    mock({
+      '/.hg': {},
+      '/other-dir': {},
+    });
+
+    prettyQuick('/other-dir');
+    expect(execa.sync).toHaveBeenCalledWith(
+      'hg',
+      ['debugancestor', 'tip', 'default'],
+      { cwd: '/' }
+    );
+  });
+
+  test('calls `hg status` with revision', () => {
+    mock({
+      '/.hg': {},
+    });
+
+    prettyQuick('root', { since: 'banana' });
+
+    expect(execa.sync).toHaveBeenCalledWith(
+      'hg',
+      ['status', '-n', '-a', '-m', '--rev', 'banana'],
+      { cwd: '/' }
+    );
+  });
+
+  test('calls onFoundSinceRevision with return value from `hg debugancestor`', () => {
+    const onFoundSinceRevision = jest.fn();
+
+    mock({
+      '/.hg': {},
+    });
+    execa.sync.mockReturnValue({ stdout: 'banana' });
+
+    prettyQuick('root', { onFoundSinceRevision });
+
+    expect(onFoundSinceRevision).toHaveBeenCalledWith('hg', 'banana');
+  });
+
+  test('calls onFoundChangedFiles with changed files', () => {
+    const onFoundChangedFiles = jest.fn();
+    mockHgFs();
+
+    prettyQuick('root', { since: 'banana', onFoundChangedFiles });
+
+    expect(onFoundChangedFiles).toHaveBeenCalledWith(['./foo.js', './bar.md']);
+  });
+
+  test('calls onWriteFile with changed files', () => {
+    const onWriteFile = jest.fn();
+    mockHgFs();
+
+    prettyQuick('root', { since: 'banana', onWriteFile });
+
+    expect(onWriteFile).toHaveBeenCalledWith('./foo.js');
+    expect(onWriteFile).toHaveBeenCalledWith('./bar.md');
+  });
+
+  test('writes formatted files to disk', () => {
+    const onWriteFile = jest.fn();
+
+    mockHgFs();
+
+    prettyQuick('root', { since: 'banana', onWriteFile });
+
+    expect(fs.readFileSync('/foo.js', 'utf8')).toEqual('formatted:foo()');
+    expect(fs.readFileSync('/bar.md', 'utf8')).toEqual('formatted:# foo');
+  });
+
+  test('without --staged does NOT stage changed files', () => {
+    mockHgFs();
+
+    prettyQuick('root', { since: 'banana' });
+
+    expect(execa.sync).not.toHaveBeenCalledWith('hg', ['add', './foo.js'], {
+      cwd: '/',
+    });
+    expect(execa.sync).not.toHaveBeenCalledWith('hg', ['add', './bar.md'], {
+      cwd: '/',
+    });
+  });
+});
diff --git a/src/scms/hg.js b/src/scms/hg.js
new file mode 100644
index 0000000..37a074c
--- /dev/null
+++ b/src/scms/hg.js
@@ -0,0 +1,40 @@
+import findUp from 'find-up';
+import execa from 'execa';
+import { dirname } from 'path';
+
+export const name = 'hg';
+
+export const detect = directory => {
+  const hgDirectory = findUp.sync('.hg', { cwd: directory });
+  if (hgDirectory) {
+    return dirname(hgDirectory);
+  }
+};
+
+const runHg = (directory, args) =>
+  execa.sync('hg', args, {
+    cwd: directory,
+  });
+
+const getLines = execaResult => execaResult.stdout.split('\n');
+
+export const getSinceRevision = (directory, { branch }) => {
+  const revision = runHg(directory, [
+    'debugancestor',
+    'tip',
+    branch || 'default',
+  ]).stdout.trim();
+  return runHg(directory, ['id', '-i', '-r', revision]).stdout.trim();
+};
+
+export const getChangedFiles = (directory, revision) => {
+  return [
+    ...getLines(
+      runHg(directory, ['status', '-n', '-a', '-m', '--rev', revision])
+    ),
+  ].filter(Boolean);
+};
+
+export const stageFile = (directory, file) => {
+  runHg(directory, ['add', file]);
+};
diff --git a/src/scms/index.js b/src/scms/index.js
index abcb6d2..cfc6f39 100644
--- a/src/scms/index.js
+++ b/src/scms/index.js
@@ -1,6 +1,7 @@
 import * as gitScm from './git';
+import * as hgScm from './hg';
 
-const scms = [gitScm];
+const scms = [gitScm, hgScm];
 
 export default directory => {
   for (const scm of scms) {