diff --git a/.cirrus.yml b/.cirrus.yml
deleted file mode 100644
index 8ed1c029d54..00000000000
--- a/.cirrus.yml
+++ /dev/null
@@ -1,81 +0,0 @@
-common_steps_template: &COMMON_STEPS_TEMPLATE
-  clone_dmd_script: |
-    set -uexo pipefail
-    git clone --branch "${CIRRUS_BASE_BRANCH:-$CIRRUS_BRANCH}" --depth 1 https://github.com/dlang/dmd.git ../dmd
-  install_prerequisites_script: cd ../dmd && ./ci/cirrusci.sh
-  install_host_compiler_script: cd ../dmd && ./ci/run.sh install_host_compiler
-  setup_repos_script: |
-    set -uexo pipefail
-    ln -s $CIRRUS_WORKING_DIR ../phobos
-    cd ../dmd && ./ci/run.sh setup_repos "${CIRRUS_BASE_BRANCH:-$CIRRUS_BRANCH}"
-  build_script: cd ../dmd && ./ci/run.sh build
-  test_dmd_script: cd ../dmd && ./ci/run.sh test_dmd
-  test_druntime_script: cd ../dmd && ./ci/run.sh test_druntime
-  test_phobos_script: cd ../dmd && ./ci/run.sh test_phobos
-
-environment:
-  CIRRUS_CLONE_DEPTH: 1
-  # for ci/run.sh:
-  MODEL: 64
-  HOST_DMD: dmd
-  N: 4
-  OS_NAME: linux
-  FULL_BUILD: false
-
-# Linux
-linux_task:
-  name: Ubuntu 18.04 $TASK_NAME_SUFFIX
-  container:
-    image: ubuntu:18.04
-    cpu: 4
-    memory: 8G
-  timeout_in: 60m
-  environment:
-    matrix:
-      - TASK_NAME_SUFFIX: x86
-        MODEL: 32
-      - TASK_NAME_SUFFIX: x64
-  install_git_script: apt-get -q update && apt-get install -yq git-core
-  << : *COMMON_STEPS_TEMPLATE
-
-# Mac
-macos_task:
-  name: macOS 12.x x64 (M1)
-  macos_instance:
-    image: ghcr.io/cirruslabs/macos-monterey-xcode:latest
-  timeout_in: 60m
-  environment:
-    OS_NAME: darwin
-    # override Cirrus default OS (`darwin`)
-    OS: osx
-  << : *COMMON_STEPS_TEMPLATE
-
-# FreeBSD
-freebsd13_task:
-  name: FreeBSD 13.0 x64
-  freebsd_instance:
-    image_family: freebsd-13-0
-    cpu: 4
-    memory: 8G
-  timeout_in: 60m
-  environment:
-    OS_NAME: freebsd
-    CI_DFLAGS: -version=TARGET_FREEBSD13
-  install_bash_and_git_script: pkg install -y bash git
-  << : *COMMON_STEPS_TEMPLATE
-
-freebsd12_task:
-  name: FreeBSD 12.3 x64
-  freebsd_instance:
-    image_family: freebsd-12-3
-    cpu: 4
-    memory: 8G
-  timeout_in: 60m
-  environment:
-    OS_NAME: freebsd
-    HOST_DMD: dmd-2.095.0
-    CI_DFLAGS: -version=TARGET_FREEBSD12
-  install_bash_and_git_script: |
-    sed -i '' -e 's|pkg.FreeBSD.org|mirrors.xtom.com/freebsd-pkg|' /etc/pkg/FreeBSD.conf
-    pkg install -y bash git
-  << : *COMMON_STEPS_TEMPLATE
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
new file mode 100644
index 00000000000..94d0d0b9c3b
--- /dev/null
+++ b/.github/workflows/main.yml
@@ -0,0 +1,170 @@
+# very similar to the DMD script: https://github.com/dlang/dmd/blob/master/.github/workflows/main.yml
+
+name: Main
+on:
+  - pull_request # without merge conflicts
+  - push # branch or tag
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  posix:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          # Linux
+          - job_name: Ubuntu 22.04 x64
+            os: ubuntu-22.04
+          - job_name: Ubuntu 22.04 x86
+            os: ubuntu-22.04
+            model: 32
+          # macOS
+          - job_name: macOS 13 x64
+            os: macos-13
+          - job_name: macOS 12 x64
+            os: macos-12
+    name: ${{ matrix.job_name }}
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 40
+    env:
+      # for ci/run.sh:
+      OS_NAME: ${{ startsWith(matrix.os, 'ubuntu') && 'linux' || (startsWith(matrix.os, 'macos') && 'darwin' || '') }}
+      MODEL: ${{ matrix.model || '64' }}
+      HOST_DMD: dmd
+      N: ${{ startsWith(matrix.os, 'macos') && '3' || '2' }}
+      FULL_BUILD: false
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 50
+      # d_do_test.d's `$p:` is buggy and chokes on the default `/Users/runner/work/phobos/phobos` path...
+      - name: Move repo to parent dir (a workaround)
+        run: mv -f * ../
+      - name: Clone DMD
+        run: |
+          set -uexo pipefail
+          cd ..
+
+          ref='${{ github.ref }}'
+          if [[ "$ref" =~ ^refs/pull/ ]]; then
+            # PR: clone the DMD head with the same name as this Phobos PR's target branch
+            # e.g., DMD stable when targeting Phobos stable
+            REPO_BRANCH="$GITHUB_BASE_REF"
+          elif [[ "$ref" =~ ^refs/(heads|tags)/(.*)$ ]]; then
+            # no PR: clone the DMD head with the same name as this Phobos head
+            # e.g., DMD stable for a push to Phobos stable, or DMD v2.105.2 for Phobos tag v2.105.2
+            REPO_BRANCH="${BASH_REMATCH[2]}"
+          else
+            echo "Error: unexpected GitHub ref '$ref'" >&2
+            exit 1
+          fi
+
+          git clone --branch "$REPO_BRANCH" --depth 1 https://github.com/dlang/dmd.git ../dmd
+      - name: Install prerequisites
+        run: cd ../../dmd && ${{ runner.os == 'macOS' && 'ci/cirrusci.sh' || 'sudo -E ci/cirrusci.sh' }}
+      - name: Install host compiler
+        run: cd ../../dmd && ci/run.sh install_host_compiler
+      - name: Build
+        run: cd ../../dmd && ci/run.sh build
+      - name: Test dmd
+        run: cd ../../dmd && ci/run.sh test_dmd
+      - name: Test druntime
+        run: cd ../../dmd && ci/run.sh test_druntime
+      - name: Test phobos
+        run: cd ../../dmd && ci/run.sh test_phobos
+
+  freebsd-vm:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - job_name: FreeBSD 13.2 x64
+            freebsd_version: '13.2'
+          - job_name: FreeBSD 12.4 x64
+            freebsd_version: '12.4'
+    name: ${{ matrix.job_name }}
+    runs-on: macos-latest
+    timeout-minutes: 60
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 50
+      - name: Run in VM
+        uses: cross-platform-actions/action@v0.21.0
+        with:
+          operating_system: freebsd
+          hypervisor: qemu
+          memory: 8G
+          sync_files: runner-to-vm
+          version: ${{ matrix.freebsd_version }}
+          shell: bash
+          run: |
+            set -uexo pipefail
+
+            freebsd_version='${{ matrix.freebsd_version }}'
+            freebsd_major="${freebsd_version:0:2}"
+
+            export OS_NAME=freebsd
+            export MODEL=64
+            export HOST_DMD=dmd
+            export N=3
+            export FULL_BUILD=false
+            export CI_DFLAGS="-version=TARGET_FREEBSD${freebsd_major}"
+
+            #if [[ "$freebsd_major" == 12 ]]; then
+            #  sudo sed -i '' -e 's|pkg.FreeBSD.org|mirrors.xtom.com/freebsd-pkg|' /etc/pkg/FreeBSD.conf
+            #fi
+
+            bash --version
+
+            echo '::group::Install git'
+            sudo pkg install -y git
+            echo '::endgroup::'
+
+            echo '::group::Move repo to parent dir (a workaround)'
+            mv -f * ../
+            cd ..
+            echo '::endgroup::'
+
+            echo '::group::Clone DMD'
+            ref='${{ github.ref }}'
+            if [[ "$ref" =~ ^refs/pull/ ]]; then
+              REPO_BRANCH="$GITHUB_BASE_REF"
+            elif [[ "$ref" =~ ^refs/(heads|tags)/(.*)$ ]]; then
+              REPO_BRANCH="${BASH_REMATCH[2]}"
+            else
+              echo "Error: unexpected GitHub ref '$ref'" >&2
+              exit 1
+            fi
+
+            git clone --branch "$REPO_BRANCH" --depth 1 https://github.com/dlang/dmd.git ../dmd
+            echo '::endgroup::'
+
+            cd ../dmd
+
+            echo '::group::Install prerequisites'
+            sudo -E ci/cirrusci.sh
+            echo '::endgroup::'
+
+            echo '::group::Install host compiler'
+            ci/run.sh install_host_compiler
+            echo '::endgroup::'
+
+            echo '::group::Build'
+            ci/run.sh build
+            echo '::endgroup::'
+
+            echo '::group::Test dmd'
+            ci/run.sh test_dmd
+            echo '::endgroup::'
+
+            echo '::group::Test druntime'
+            ci/run.sh test_druntime
+            echo '::endgroup::'
+
+            echo '::group::Test phobos'
+            ci/run.sh test_phobos
+            echo '::endgroup::'