diff --git a/.github/workflows/cpp.yml b/.github/workflows/cpp.yml
index 3effb88b606e..74747efad5b5 100644
--- a/.github/workflows/cpp.yml
+++ b/.github/workflows/cpp.yml
@@ -75,7 +75,7 @@ jobs:
     name: ${{ matrix.title }}
     runs-on: ${{ matrix.runs-on }}
     if: ${{ !contains(github.event.pull_request.title, 'WIP') }}
-    timeout-minutes: 75
+    timeout-minutes: ${{ matrix.timeout || 75 }}
     strategy:
       fail-fast: false
       matrix:
@@ -102,6 +102,15 @@ jobs:
             runs-on: ubuntu-24.04-arm
             title: ARM64 Ubuntu 22.04 C++
             ubuntu: 22.04
+          - arch: riscv64
+            clang-tools: 18
+            image: ubuntu-cpp
+            llvm: 18
+            runs-on: ubuntu-24.04-riscv
+            timeout: 300
+            title: RISCV64 Ubuntu 24.04 C++
+            ubuntu: 24.04
+            buildkit: "0"
     env:
       ARCH: ${{ matrix.arch }}
       ARROW_SIMD_LEVEL: ${{ matrix.simd-level }}
@@ -128,17 +137,32 @@ jobs:
           python-version: 3
       - name: Setup Python on self-hosted runner
         if: |
-          contains(matrix.runs-on, 'self-hosted')
+          contains(matrix.runs-on, 'self-hosted') ||
+          matrix.arch == 'riscv64'
         run: |
           sudo apt update
           sudo apt install -y --no-install-recommends python3 python3-dev python3-pip
-          python3 -m pip install -U pip
+          python3 -m pip install --break-system-packages -U pip
+          echo "$HOME/.local/bin" >> $GITHUB_PATH
+      - name: Setup Docker on RISE runner
+        if: matrix.arch == 'riscv64'
+        run: |
+          # Install Docker Compose v2 plugin (not in Ubuntu riscv64 repos)
+          # Can't upgrade Docker daemon mid-job (no systemd to restart)
+          # so we disable BuildKit to work around the HTTP/HTTPS issue
+          COMPOSE_VERSION="v5.1.1"
+          sudo mkdir -p /usr/local/lib/docker/cli-plugins
+          sudo curl -SL "https://github.com/docker/compose/releases/download/${COMPOSE_VERSION}/docker-compose-linux-riscv64" \
+            -o /usr/local/lib/docker/cli-plugins/docker-compose
+          sudo chmod +x /usr/local/lib/docker/cli-plugins/docker-compose
+          docker compose version
       - name: Setup Archery
-        run: python3 -m pip install -e dev/archery[docker]
+        run: python3 -m pip install --break-system-packages -e dev/archery[docker]
       - name: Execute Docker Build
         env:
           ARCHERY_DOCKER_USER: ${{ secrets.DOCKERHUB_USER }}
           ARCHERY_DOCKER_PASSWORD: ${{ secrets.DOCKERHUB_TOKEN }}
+          DOCKER_BUILDKIT: ${{ matrix.buildkit || '1' }}
         run: |
           # GH-40558: reduce ASLR to avoid ASAN/LSAN crashes
           sudo sysctl -w vm.mmap_rnd_bits=28
diff --git a/ci/scripts/install_minio.sh b/ci/scripts/install_minio.sh
index 5efa03e82e20..5a7d05fc11a4 100755
--- a/ci/scripts/install_minio.sh
+++ b/ci/scripts/install_minio.sh
@@ -34,7 +34,7 @@ archs=([x86_64]=amd64
        [s390x]=s390x)
 
 arch=$(uname -m)
-if [ -z "${archs[$arch]}" ]; then
+if [ -z "${archs[$arch]:-}" ]; then
   echo "Unsupported architecture: ${arch}"
   exit 0
 fi