diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..142e0ee
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,57 @@
+name: Continuous Integration
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - ubuntu-latest
+          - ubuntu-20.04
+        php-version:
+          # - 7.1
+          - 7.2
+          - 7.3
+          - 8.0
+          - 8.1
+          - 8.2
+          - 8.3
+          - 8.4
+    steps:
+      - name: Install dependencies (Ubuntu)
+        if: runner.os == 'Linux'
+        run: |-
+          sudo apt-get update
+          sudo apt-get install -y build-essential curl openssl
+
+      - uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-version }}
+          extensions: libsodium-1.0.2
+          # tools: phpunit:4.x
+
+      - name: Cache multiple paths
+        uses: actions/cache@v4
+        with:
+          path: |-
+            $HOME/libsodium
+            vendor
+          key: ${{ runner.os }}-php-${{ hashFiles('composer.json') }}
+          restore-keys: |
+            ${{ runner.os }}-php-
+
+      - uses: actions/checkout@v4
+      - name: Install PHP dependencies
+        run: |-
+          composer selfupdate
+          sed -i s#\>=5.4.0#\>=5.3.0#g composer.json
+          composer install --prefer-source --no-ansi --no-interaction
+
+      - name: Run tests
+        run: php vendor/bin/phpunit
+