diff --git a/.github/workflows/test-packages-input.yml b/.github/workflows/test-packages-input.yml
new file mode 100644
index 0000000..2a83f9c
--- /dev/null
+++ b/.github/workflows/test-packages-input.yml
@@ -0,0 +1,113 @@
+name: Test Packages Input
+
+# This workflow is a black-box integration test for the action's `packages` input.
+#
+# The fixture workspace contains three crates (package-a/package-b/package-c). Each crate writes a
+# marker file (marker-package-*) when its tests run. We assert marker presence/absence to prove
+# that:
+# - when `packages` is empty, the action runs the whole workspace (`--all`)
+# - when `packages` is provided, the action uses `-p <pkg>` and only runs those packages
+#
+# The fixture workspace also sets `default-members = ["package-a"]` to catch regressions where
+# the action accidentally stops passing `--all` for the default (empty packages) case.
+
+on:
+  workflow_dispatch:
+  pull_request:
+    branches: [v1-master]
+    paths:
+      - "action.yml"
+      - "README.MD"
+      - ".github/workflows/test-packages-input.yml"
+      - "tests/fixtures/packages-input-workspace/**"
+
+jobs:
+  packages-input:
+    name: Packages Input - ${{ matrix.name }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - name: cargo empty (default all)
+            target: x86_64-unknown-linux-gnu
+            use_cross: false
+            use_tarpaulin: false
+            packages: ""
+            expect: "marker-package-a marker-package-b marker-package-c"
+            forbid: ""
+
+          - name: cargo single
+            target: x86_64-unknown-linux-gnu
+            use_cross: false
+            use_tarpaulin: false
+            packages: |
+              package-b
+            expect: "marker-package-b"
+            forbid: "marker-package-a marker-package-c"
+
+          - name: cargo multiple
+            target: x86_64-unknown-linux-gnu
+            use_cross: false
+            use_tarpaulin: false
+            packages: |
+              package-a
+              package-c
+            expect: "marker-package-a marker-package-c"
+            forbid: "marker-package-b"
+
+          - name: cross multiple
+            target: aarch64-unknown-linux-gnu
+            use_cross: true
+            use_tarpaulin: false
+            packages: |
+              package-a
+              package-c
+            expect: "marker-package-a marker-package-c"
+            forbid: "marker-package-b"
+
+          - name: tarpaulin single
+            target: x86_64-unknown-linux-gnu
+            use_cross: false
+            use_tarpaulin: true
+            packages: |
+              package-b
+            expect: "marker-package-b"
+            forbid: "marker-package-a marker-package-c"
+
+    steps:
+      - name: Checkout Action Repository
+        uses: actions/checkout@v6
+
+      - name: Clean package markers
+        shell: bash
+        run: rm -f tests/fixtures/packages-input-workspace/marker-package-*
+
+      - name: Run action
+        uses: ./
+        with:
+          rust-project-path: tests/fixtures/packages-input-workspace
+          rust-toolchain: stable
+          target: ${{ matrix.target }}
+          use-cross: ${{ matrix.use_cross }}
+          use-tarpaulin: ${{ matrix.use_tarpaulin }}
+          upload-coverage: false
+          packages: ${{ matrix.packages }}
+
+      - name: Assert markers
+        shell: bash
+        run: |
+          set -euo pipefail
+          root="tests/fixtures/packages-input-workspace"
+          expect="${{ matrix.expect }}"
+          forbid="${{ matrix.forbid }}"
+
+          for f in $expect; do
+            test -f "$root/$f" || { echo "Missing marker: $f"; exit 1; }
+          done
+
+          if [ -n "$forbid" ]; then
+            for f in $forbid; do
+              test ! -f "$root/$f" || { echo "Unexpected marker: $f"; exit 1; }
+            done
+          fi
diff --git a/README.MD b/README.MD
index 7fe0a6d..ce1470e 100644
--- a/README.MD
+++ b/README.MD
@@ -46,6 +46,9 @@ To use this action in your GitHub workflow, add the following step:
     codecov-flags: 'unittests'
     codecov-name: 'codecov-umbrella'
     features: 'feature1 feature2'
+    packages: |
+      package-a
+      package-b
     no-default-features: false
     use-cross: false
     additional-test-args: '--ignored --test-threads=1'
@@ -70,6 +73,7 @@ To use this action in your GitHub workflow, add the following step:
 | `codecov-flags`             | Flags to pass to Codecov                                                                           | No       | `'unittests'`        |
 | `codecov-name`              | Custom defined name for the upload                                                                 | No       | `'codecov-umbrella'` |
 | `features`                  | Space-separated list of features to enable during testing                                          | No       | `''`                 |
+| `packages`                  | Multi-line list of package names to test (one per line). If empty, tests all packages in workspace | No       | `''`                 |
 | `no-default-features`       | Disable default features during testing                                                            | No       | `false`              |
 | `use-cross`                 | Use cross-rs for testing. If false, use cargo.                                                     | No       | `false`              |
 | `additional-test-args`      | Additional arguments to pass to the cargo test command                                             | No       | `''`                 |
@@ -204,4 +208,4 @@ rust-toolchain: 'beta'
 
 This GitHub Action is released under the [MIT License](LICENSE).
 
-[rust-lw-binary]: https://github.com/Reloaded-Project/devops-rust-lightweight-binary
\ No newline at end of file
+[rust-lw-binary]: https://github.com/Reloaded-Project/devops-rust-lightweight-binary
diff --git a/action.yml b/action.yml
index 9b6d4c6..c326728 100644
--- a/action.yml
+++ b/action.yml
@@ -77,6 +77,11 @@ inputs:
     required: false
     default: ""
 
+  packages:
+    description: "Multi-line list of package names to test (one per line). If empty, tests all packages in workspace (--all)"
+    required: false
+    default: ""
+
 runs:
   using: "composite"
   steps:
@@ -90,6 +95,27 @@ runs:
         fi
         echo "SAFE_ADDITIONAL_TEST_ARGS=${SAFE_ADDITIONAL_TEST_ARGS}" >> $GITHUB_ENV
 
+        # Process packages input - convert multiline to space-separated, clean whitespace
+        SAFE_PACKAGES=$(echo "${{ inputs.packages }}" | tr -d '\r' | tr '\n\t' '  ' | tr -s ' ' | sed 's/^ *//;s/ *$//')
+        echo "SAFE_PACKAGES=${SAFE_PACKAGES}" >> $GITHUB_ENV
+
+        # Build packages argument once and reuse across steps
+        if [ -n "$SAFE_PACKAGES" ]; then
+          PACKAGES_ARG=""
+          for pkg in $SAFE_PACKAGES; do
+            if [ -n "$pkg" ]; then
+              if [ -z "$PACKAGES_ARG" ]; then
+                PACKAGES_ARG="-p $pkg"
+              else
+                PACKAGES_ARG="$PACKAGES_ARG -p $pkg"
+              fi
+            fi
+          done
+        else
+          PACKAGES_ARG="--all"
+        fi
+        echo "PACKAGES_ARG=${PACKAGES_ARG}" >> $GITHUB_ENV
+
     - name: Install Rust Toolchain
       if: inputs.install-rust-toolchain == 'true'
       uses: actions-rust-lang/setup-rust-toolchain@v1
@@ -164,7 +190,7 @@ runs:
       shell: bash
       working-directory: ${{ inputs.rust-project-path }}
       run: |
-        cargo +${{ inputs.rust-toolchain }} tarpaulin --all --out xml --engine llvm \
+        cargo +${{ inputs.rust-toolchain }} tarpaulin $PACKAGES_ARG --out xml --engine llvm \
           --features "${{ inputs.features }}" \
           ${{ inputs.no-default-features == 'true' && '--no-default-features' || '' }} \
           ${{ inputs.target != '' && format('--target "{0}"', inputs.target) || '' }} \
@@ -177,7 +203,7 @@ runs:
       shell: bash
       working-directory: ${{ inputs.rust-project-path }}
       run: |
-        cargo +${{ inputs.rust-toolchain }} test --all \
+        cargo +${{ inputs.rust-toolchain }} test $PACKAGES_ARG \
           --features "${{ inputs.features }}" \
           ${{ inputs.no-default-features == 'true' && '--no-default-features' || '' }} \
           ${{ inputs.target != '' && format('--target "{0}"', inputs.target) || '' }} \
@@ -190,7 +216,7 @@ runs:
       # the RUSTFLAGS are a hack around cross build errors on certain setups
       # https://github.com/cross-rs/cross/issues/1561
       run: |
-        RUSTFLAGS="" cross +${{ inputs.rust-toolchain }} test --all \
+        RUSTFLAGS="" cross +${{ inputs.rust-toolchain }} test $PACKAGES_ARG \
           --features "${{ inputs.features }}" \
           ${{ inputs.no-default-features == 'true' && '--no-default-features' || '' }} \
           ${{ inputs.target != '' && format('--target "{0}"', inputs.target) || '' }} \
diff --git a/tests/fixtures/packages-input-workspace/Cargo.lock b/tests/fixtures/packages-input-workspace/Cargo.lock
new file mode 100644
index 0000000..86db68e
--- /dev/null
+++ b/tests/fixtures/packages-input-workspace/Cargo.lock
@@ -0,0 +1,15 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "package-a"
+version = "0.1.0"
+
+[[package]]
+name = "package-b"
+version = "0.1.0"
+
+[[package]]
+name = "package-c"
+version = "0.1.0"
diff --git a/tests/fixtures/packages-input-workspace/Cargo.toml b/tests/fixtures/packages-input-workspace/Cargo.toml
new file mode 100644
index 0000000..9ef3c0f
--- /dev/null
+++ b/tests/fixtures/packages-input-workspace/Cargo.toml
@@ -0,0 +1,13 @@
+[workspace]
+resolver = "2"
+members = [
+  "package-a",
+  "package-b",
+  "package-c",
+]
+
+# If the action accidentally drops `--all`, this makes the default behavior
+# run only package-a. Our CI checks rely on this to detect regressions.
+default-members = [
+  "package-a",
+]
diff --git a/tests/fixtures/packages-input-workspace/package-a/Cargo.toml b/tests/fixtures/packages-input-workspace/package-a/Cargo.toml
new file mode 100644
index 0000000..63162a0
--- /dev/null
+++ b/tests/fixtures/packages-input-workspace/package-a/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "package-a"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[lib]
+path = "src/lib.rs"
diff --git a/tests/fixtures/packages-input-workspace/package-a/src/lib.rs b/tests/fixtures/packages-input-workspace/package-a/src/lib.rs
new file mode 100644
index 0000000..0fd07c3
--- /dev/null
+++ b/tests/fixtures/packages-input-workspace/package-a/src/lib.rs
@@ -0,0 +1,17 @@
+#[cfg(test)]
+mod tests {
+    use std::fs;
+    use std::path::PathBuf;
+
+    fn workspace_root() -> PathBuf {
+        PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+            .parent()
+            .expect("package directory should have a workspace root parent")
+            .to_path_buf()
+    }
+
+    #[test]
+    fn writes_marker() {
+        fs::write(workspace_root().join("marker-package-a"), "ok\n").unwrap();
+    }
+}
diff --git a/tests/fixtures/packages-input-workspace/package-b/Cargo.toml b/tests/fixtures/packages-input-workspace/package-b/Cargo.toml
new file mode 100644
index 0000000..9807a3f
--- /dev/null
+++ b/tests/fixtures/packages-input-workspace/package-b/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "package-b"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[lib]
+path = "src/lib.rs"
diff --git a/tests/fixtures/packages-input-workspace/package-b/src/lib.rs b/tests/fixtures/packages-input-workspace/package-b/src/lib.rs
new file mode 100644
index 0000000..27f6b8f
--- /dev/null
+++ b/tests/fixtures/packages-input-workspace/package-b/src/lib.rs
@@ -0,0 +1,17 @@
+#[cfg(test)]
+mod tests {
+    use std::fs;
+    use std::path::PathBuf;
+
+    fn workspace_root() -> PathBuf {
+        PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+            .parent()
+            .expect("package directory should have a workspace root parent")
+            .to_path_buf()
+    }
+
+    #[test]
+    fn writes_marker() {
+        fs::write(workspace_root().join("marker-package-b"), "ok\n").unwrap();
+    }
+}
diff --git a/tests/fixtures/packages-input-workspace/package-c/Cargo.toml b/tests/fixtures/packages-input-workspace/package-c/Cargo.toml
new file mode 100644
index 0000000..3658c0f
--- /dev/null
+++ b/tests/fixtures/packages-input-workspace/package-c/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "package-c"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[lib]
+path = "src/lib.rs"
diff --git a/tests/fixtures/packages-input-workspace/package-c/src/lib.rs b/tests/fixtures/packages-input-workspace/package-c/src/lib.rs
new file mode 100644
index 0000000..3f72cbc
--- /dev/null
+++ b/tests/fixtures/packages-input-workspace/package-c/src/lib.rs
@@ -0,0 +1,17 @@
+#[cfg(test)]
+mod tests {
+    use std::fs;
+    use std::path::PathBuf;
+
+    fn workspace_root() -> PathBuf {
+        PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+            .parent()
+            .expect("package directory should have a workspace root parent")
+            .to_path_buf()
+    }
+
+    #[test]
+    fn writes_marker() {
+        fs::write(workspace_root().join("marker-package-c"), "ok\n").unwrap();
+    }
+}