diff --git a/barrage/__main__.py b/barrage/__main__.py
index 0fe34bb..66a177a 100644
--- a/barrage/__main__.py
+++ b/barrage/__main__.py
@@ -27,6 +27,10 @@
     python3 -m barrage --max-concurrency 4 test/
     python3 -m barrage -i test/test_example.py::MyTestClass::test_method
     python3 -m barrage -x test/
+
+    # Set a test directory (used as default search dir and import root)
+    python3 -m barrage -t tests/
+    python3 -m barrage --top-level-directory tests/ test_foo.py::MyClass::test_method
 """
 
 import argparse
@@ -100,23 +104,40 @@ def main(argv: list[str] | None = None) -> int:
         default="test_*.py",
         help="Pattern to match test files when discovering in directories (default: test_*.py)",
     )
+    parser.add_argument(
+        "-t",
+        "--top-level-directory",
+        default=None,
+        dest="top_level_directory",
+        metavar="DIR",
+        help=(
+            "Top-level directory for test discovery and imports.  "
+            "When no positional paths are given, tests are discovered "
+            "in this directory instead of the current directory.  "
+            "When paths are given, relative paths are resolved against "
+            "this directory and it is used as the import root."
+        ),
+    )
     parser.add_argument(
         "paths",
         nargs="*",
-        default=["."],
+        default=None,
         metavar="path",
         help=(
             "Paths to test files or directories.  A path may be suffixed "
             "with ::ClassName to select a single test class, or "
             "::ClassName::test_method to select a single test.  "
             "When no paths are given, discovers tests in the current "
-            "directory."
+            "directory (or -t if set)."
         ),
     )
 
     args = parser.parse_args(argv)
 
-    suite = resolve_tests(args.paths, pattern=args.pattern)
+    paths = args.paths if args.paths else [args.top_level_directory or "."]
+    top_level_dir = args.top_level_directory
+
+    suite = resolve_tests(paths, pattern=args.pattern, top_level_dir=top_level_dir)
 
     if not suite.entries:
         print("No tests discovered.", file=sys.stderr)
diff --git a/barrage/discovery.py b/barrage/discovery.py
index 55f48c6..8ba36da 100644
--- a/barrage/discovery.py
+++ b/barrage/discovery.py
@@ -14,6 +14,7 @@
 def resolve_tests(
     path_specs: list[str],
     pattern: str = "test_*.py",
+    top_level_dir: str | None = None,
 ) -> AsyncTestSuite:
     """
     Build an :class:`AsyncTestSuite` from a list of path specifications.
@@ -40,6 +41,11 @@ def resolve_tests(
     pattern:
         Glob pattern for test file names used during directory
         discovery (default ``test_*.py``).
+    top_level_dir:
+        Top-level directory of the project, used as the import root
+        for discovered modules.  When ``None``, directory discovery
+        uses *start_dir* and file discovery uses the current working
+        directory.
 
     Returns
     -------
@@ -54,6 +60,7 @@ def resolve_tests(
         ``SystemExit(2)`` is raised.
     """
     suite = AsyncTestSuite()
+    top = Path(top_level_dir) if top_level_dir else None
 
     for spec in path_specs:
         parts = spec.split("::")
@@ -70,6 +77,14 @@ def resolve_tests(
 
         p = Path(path_str)
 
+        # When a top-level directory is set and the path is not
+        # absolute, resolve it relative to that directory so that
+        # ``-t test test_file.py::Class`` finds ``test/test_file.py``.
+        if top and not p.is_absolute() and not p.exists():
+            candidate = top / p
+            if candidate.exists():
+                p = candidate
+
         if p.is_dir():
             if class_name is not None:
                 print(
@@ -77,7 +92,7 @@ def resolve_tests(
                     file=sys.stderr,
                 )
                 raise SystemExit(2)
-            _discover_directory(p, suite, pattern=pattern)
+            _discover_directory(p, suite, pattern=pattern, top_level_dir=top)
 
         elif p.is_file():
             _discover_file(
@@ -85,6 +100,7 @@ def resolve_tests(
                 suite,
                 class_name=class_name,
                 method_name=method_name,
+                top_level_dir=top,
             )
 
         else:
@@ -176,6 +192,7 @@ def _discover_file(
     suite: AsyncTestSuite,
     class_name: str | None = None,
     method_name: str | None = None,
+    top_level_dir: Path | None = None,
 ) -> None:
     """Import *filepath* and add matching test classes/methods to *suite*.
 
@@ -189,12 +206,16 @@ def _discover_file(
         If given, only the class with this name is collected.
     method_name:
         If given (requires *class_name*), only this method is collected.
+    top_level_dir:
+        Top-level directory used as the import root.  When ``None``,
+        the current working directory is used.
     """
     filepath = filepath.resolve()
 
-    # Use the current working directory as the top-level import root so
-    # that ``test/test_foo.py`` imports as ``test.test_foo``.
-    top = Path.cwd().resolve()
+    # Use the provided top-level directory or fall back to the current
+    # working directory as the import root so that ``test/test_foo.py``
+    # imports as ``test.test_foo``.
+    top = top_level_dir.resolve() if top_level_dir else Path.cwd().resolve()
     if str(top) not in sys.path:
         sys.path.insert(0, str(top))
 
diff --git a/tests/test_framework.py b/tests/test_framework.py
index e450690..86dd4e2 100644
--- a/tests/test_framework.py
+++ b/tests/test_framework.py
@@ -1287,6 +1287,65 @@ async def test_resolve_non_test_class(self) -> None:
         assert isinstance(ctx.exception, SystemExit)
         self.assertEqual(ctx.exception.code, 2)
 
+    # ── top_level_dir ─────────────────────────────────────────────────
+
+    async def test_resolve_top_level_dir_discovers_directory(self) -> None:
+        """``top_level_dir`` used as discovery root when passed as path."""
+        suite = resolve_tests([self._sample_dir], top_level_dir=self._sample_dir)
+        class_names = sorted(cls.__name__ for cls, _ in suite.entries)
+        self.assertIn("SamplePassingTests", class_names)
+        self.assertIn("SampleSequentialTests", class_names)
+        total_methods = sum(len(m) for _, m in suite.entries)
+        self.assertEqual(total_methods, 4)
+
+    async def test_resolve_top_level_dir_relative_file(self) -> None:
+        """A relative file path is resolved against ``top_level_dir``."""
+        suite = resolve_tests(["test_sample.py"], top_level_dir=self._sample_dir)
+        class_names = sorted(cls.__name__ for cls, _ in suite.entries)
+        self.assertIn("SamplePassingTests", class_names)
+        self.assertIn("SampleSequentialTests", class_names)
+
+    async def test_resolve_top_level_dir_relative_file_with_class(self) -> None:
+        """A relative ``file::Class`` spec is resolved against ``top_level_dir``."""
+        suite = resolve_tests(
+            ["test_sample.py::SamplePassingTests"],
+            top_level_dir=self._sample_dir,
+        )
+        self.assertEqual(len(suite.entries), 1)
+        cls, methods = suite.entries[0]
+        self.assertEqual(cls.__name__, "SamplePassingTests")
+        self.assertEqual(len(methods), 2)
+
+    async def test_resolve_top_level_dir_relative_file_with_method(self) -> None:
+        """A relative ``file::Class::method`` spec is resolved against ``top_level_dir``."""
+        suite = resolve_tests(
+            ["test_sample.py::SamplePassingTests::test_add"],
+            top_level_dir=self._sample_dir,
+        )
+        self.assertEqual(len(suite.entries), 1)
+        cls, methods = suite.entries[0]
+        self.assertEqual(cls.__name__, "SamplePassingTests")
+        self.assertEqual(methods, ["test_add"])
+
+    async def test_resolve_top_level_dir_absolute_path_ignores_top(self) -> None:
+        """An absolute path is not resolved against ``top_level_dir``."""
+        suite = resolve_tests(
+            [self._sample_file],
+            top_level_dir="/tmp/_barrage_no_such_dir_99999",
+        )
+        class_names = sorted(cls.__name__ for cls, _ in suite.entries)
+        self.assertIn("SamplePassingTests", class_names)
+
+    async def test_resolve_top_level_dir_relative_not_found(self) -> None:
+        """A relative path that doesn't exist in either cwd or top dir gives SystemExit(2)."""
+        with self.assertRaises(SystemExit) as ctx:
+            resolve_tests(
+                ["no_such_file_99999.py"],
+                top_level_dir=self._sample_dir,
+            )
+        assert isinstance(ctx.exception, SystemExit)
+        self.assertEqual(ctx.exception.code, 2)
+
 
 # ===================================================================== #
 #  17. CLI (__main__) via subprocess
@@ -1421,6 +1480,168 @@ async def test_main_nonexistent_method_exits_2(self) -> None:
         self.assertEqual(result.returncode, 2)
         self.assertIn("no_such_method", result.stderr.decode())
 
+    async def test_top_level_directory_discovers_tests(self) -> None:
+        """``-t dir`` with no positional paths discovers tests in that directory."""
+        sample_dir = str(Path(__file__).parent / "_sample_discover")
+        top_dir = str(Path(__file__).resolve().parents[1])
+
+        if not Path(sample_dir).is_dir():
+            self.skipTest("sample directory missing")
+
+        async with asyncio.timeout(30):
+            result = await run(
+                [sys.executable, "-m", "barrage", "-t", sample_dir, "-v"],
+                stdout=PIPE,
+                stderr=PIPE,
+                cwd=top_dir,
+                check=False,
+            )
+        stdout_text = result.stdout.decode()
+        self.assertEqual(result.returncode, 0, f"stdout:\n{stdout_text}\nstderr:\n{result.stderr.decode()}")
+        self.assertIn("Ran 4 test(s)", stdout_text)
+        self.assertIn("OK", stdout_text)
+
+    async def test_top_level_directory_resolves_relative_path(self) -> None:
+        """``-t dir file.py`` resolves the relative path against -t."""
+        sample_dir = str(Path(__file__).parent / "_sample_discover")
+        top_dir = str(Path(__file__).resolve().parents[1])
+
+        if not Path(sample_dir).is_dir():
+            self.skipTest("sample directory missing")
+
+        async with asyncio.timeout(30):
+            result = await run(
+                [sys.executable, "-m", "barrage", "-t", sample_dir, "test_sample.py", "-v"],
+                stdout=PIPE,
+                stderr=PIPE,
+                cwd=top_dir,
+                check=False,
+            )
+        stdout_text = result.stdout.decode()
+        self.assertEqual(result.returncode, 0, f"stdout:\n{stdout_text}\nstderr:\n{result.stderr.decode()}")
+        self.assertIn("Ran 4 test(s)", stdout_text)
+        self.assertIn("OK", stdout_text)
+
+    async def test_top_level_directory_with_class_selector(self) -> None:
+        """``-t dir file.py::Class`` resolves the file and selects the class."""
+        sample_dir = str(Path(__file__).parent / "_sample_discover")
+        top_dir = str(Path(__file__).resolve().parents[1])
+
+        if not Path(sample_dir).is_dir():
+            self.skipTest("sample directory missing")
+
+        async with asyncio.timeout(30):
+            result = await run(
+                [
+                    sys.executable,
+                    "-m",
+                    "barrage",
+                    "-t",
+                    sample_dir,
+                    "test_sample.py::SamplePassingTests",
+                    "-v",
+                ],
+                stdout=PIPE,
+                stderr=PIPE,
+                cwd=top_dir,
+                check=False,
+            )
+        stdout_text = result.stdout.decode()
+        self.assertEqual(result.returncode, 0, f"stdout:\n{stdout_text}\nstderr:\n{result.stderr.decode()}")
+        self.assertIn("Ran 2 test(s)", stdout_text)
+        self.assertIn("OK", stdout_text)
+
+    async def test_top_level_directory_with_method_selector(self) -> None:
+        """``-t dir file.py::Class::method`` resolves and selects a single test."""
+        sample_dir = str(Path(__file__).parent / "_sample_discover")
+        top_dir = str(Path(__file__).resolve().parents[1])
+
+        if not Path(sample_dir).is_dir():
+            self.skipTest("sample directory missing")
+
+        async with asyncio.timeout(30):
+            result = await run(
+                [
+                    sys.executable,
+                    "-m",
+                    "barrage",
+                    "-t",
+                    sample_dir,
+                    "test_sample.py::SamplePassingTests::test_add",
+                    "-v",
+                ],
+                stdout=PIPE,
+                stderr=PIPE,
+                cwd=top_dir,
+                check=False,
+            )
+        stdout_text = result.stdout.decode()
+        self.assertEqual(result.returncode, 0, f"stdout:\n{stdout_text}\nstderr:\n{result.stderr.decode()}")
+        self.assertIn("Ran 1 test(s)", stdout_text)
+        self.assertIn("test_add", stdout_text)
+        self.assertIn("OK", stdout_text)
+
+    async def test_top_level_directory_nonexistent_exits_2(self) -> None:
+        """``-t /nonexistent`` with no positional paths exits with code 2."""
+        top_dir = str(Path(__file__).resolve().parents[1])
+
+        async with asyncio.timeout(30):
+            result = await run(
+                [sys.executable, "-m", "barrage", "-t", "/tmp/_barrage_no_such_dir_99999"],
+                stdout=PIPE,
+                stderr=PIPE,
+                cwd=top_dir,
+                check=False,
+            )
+        self.assertEqual(result.returncode, 2)
+
+    async def test_top_level_directory_long_form(self) -> None:
+        """The long form ``--top-level-directory`` works the same as ``-t``."""
+        sample_dir = str(Path(__file__).parent / "_sample_discover")
+        top_dir = str(Path(__file__).resolve().parents[1])
+
+        if not Path(sample_dir).is_dir():
+            self.skipTest("sample directory missing")
+
+        async with asyncio.timeout(30):
+            result = await run(
+                [sys.executable, "-m", "barrage", "--top-level-directory", sample_dir, "-v"],
+                stdout=PIPE,
+                stderr=PIPE,
+                cwd=top_dir,
+                check=False,
+            )
+        stdout_text = result.stdout.decode()
+        self.assertEqual(result.returncode, 0, f"stdout:\n{stdout_text}\nstderr:\n{result.stderr.decode()}")
+        self.assertIn("Ran 4 test(s)", stdout_text)
+        self.assertIn("OK", stdout_text)
+
+    async def test_top_level_directory_with_absolute_path(self) -> None:
+        """``-t`` does not interfere when positional paths are absolute."""
+        sample_file = str(Path(__file__).parent / "_sample_discover" / "test_sample.py")
+        top_dir = str(Path(__file__).resolve().parents[1])
+
+        async with asyncio.timeout(30):
+            result = await run(
+                [
+                    sys.executable,
+                    "-m",
+                    "barrage",
+                    "-t",
+                    "/tmp/_barrage_no_such_dir_99999",
+                    sample_file,
+                    "-v",
+                ],
+                stdout=PIPE,
+                stderr=PIPE,
+                cwd=top_dir,
+                check=False,
+            )
+        stdout_text = result.stdout.decode()
+        self.assertEqual(result.returncode, 0, f"stdout:\n{stdout_text}\nstderr:\n{result.stderr.decode()}")
+        self.assertIn("Ran 4 test(s)", stdout_text)
+        self.assertIn("OK", stdout_text)
+
 
 # ===================================================================== #
 #  18. Stress test: many tests with limited concurrency