diff --git a/ngraph/__init__.py b/ngraph/__init__.py
index e69de29..22d72d2 100644
--- a/ngraph/__init__.py
+++ b/ngraph/__init__.py
@@ -0,0 +1,7 @@
+"""NetGraph package."""
+
+from __future__ import annotations
+
+from . import cli
+
+__all__ = ["cli"]
diff --git a/ngraph/__main__.py b/ngraph/__main__.py
new file mode 100644
index 0000000..fc97e39
--- /dev/null
+++ b/ngraph/__main__.py
@@ -0,0 +1,6 @@
+from __future__ import annotations
+
+from .cli import main
+
+if __name__ == "__main__":
+    main()
diff --git a/ngraph/cli.py b/ngraph/cli.py
new file mode 100644
index 0000000..932fe44
--- /dev/null
+++ b/ngraph/cli.py
@@ -0,0 +1,47 @@
+from __future__ import annotations
+
+import argparse
+import json
+from pathlib import Path
+from typing import Any, Dict, List, Optional
+
+from ngraph.scenario import Scenario
+
+
+def _run_scenario(path: Path, output: Optional[Path]) -> None:
+    """Run a scenario file and store results as JSON."""
+    yaml_text = path.read_text()
+    scenario = Scenario.from_yaml(yaml_text)
+    scenario.run()
+
+    results_dict: Dict[str, Dict[str, Any]] = scenario.results.to_dict()
+    json_str = json.dumps(results_dict, indent=2, default=str)
+    if output:
+        output.write_text(json_str)
+    else:
+        print(json_str)
+
+
+def main(argv: Optional[List[str]] = None) -> None:
+    """Entry point for the ``ngraph`` command."""
+    parser = argparse.ArgumentParser(prog="ngraph")
+    subparsers = parser.add_subparsers(dest="command", required=True)
+
+    run_parser = subparsers.add_parser("run", help="Run a scenario")
+    run_parser.add_argument("scenario", type=Path, help="Path to scenario YAML")
+    run_parser.add_argument(
+        "--results",
+        "-r",
+        type=Path,
+        default=None,
+        help="Write JSON results to this file instead of stdout",
+    )
+
+    args = parser.parse_args(argv)
+
+    if args.command == "run":
+        _run_scenario(args.scenario, args.results)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/ngraph/results.py b/ngraph/results.py
index 174d815..5422045 100644
--- a/ngraph/results.py
+++ b/ngraph/results.py
@@ -54,3 +54,7 @@ def get_all(self, key: str) -> Dict[str, Any]:
             if key in data:
                 result[step_name] = data[key]
         return result
+
+    def to_dict(self) -> Dict[str, Dict[str, Any]]:
+        """Return a dictionary representation of all stored results."""
+        return {step: data.copy() for step, data in self._store.items()}
diff --git a/pyproject.toml b/pyproject.toml
index 88212c0..bc22bb6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -33,6 +33,9 @@ dev = [
     "black",
     "isort",
 ]
+[project.scripts]
+ngraph = "ngraph.cli:main"
+
 
 # ---------------------------------------------------------------------
 # Pytest flags
diff --git a/tests/test_cli.py b/tests/test_cli.py
new file mode 100644
index 0000000..a6802e1
--- /dev/null
+++ b/tests/test_cli.py
@@ -0,0 +1,22 @@
+import json
+from pathlib import Path
+
+from ngraph import cli
+
+
+def test_cli_run_file(tmp_path: Path) -> None:
+    scenario = Path("tests/scenarios/scenario_1.yaml")
+    out_file = tmp_path / "res.json"
+    cli.main(["run", str(scenario), "--results", str(out_file)])
+    assert out_file.is_file()
+    data = json.loads(out_file.read_text())
+    assert "build_graph" in data
+    assert "graph" in data["build_graph"]
+
+
+def test_cli_run_stdout(capsys) -> None:
+    scenario = Path("tests/scenarios/scenario_1.yaml")
+    cli.main(["run", str(scenario)])
+    captured = capsys.readouterr()
+    data = json.loads(captured.out)
+    assert "build_graph" in data