diff --git a/python/grass/app/cli.py b/python/grass/app/cli.py
index 0cf05afbb47..64e7ec8cc34 100644
--- a/python/grass/app/cli.py
+++ b/python/grass/app/cli.py
@@ -27,7 +27,6 @@
 
 import grass.script as gs
 from grass.app.data import lock_mapset, unlock_mapset, MapsetLockingException
-from grass.grassdb.create import create_mapset
 from grass.exceptions import ScriptError
 from grass.tools import Tools
 
@@ -98,6 +97,11 @@ def add_mapset_subparser(subparsers):
 
     subparser = mapset_subparsers.add_parser("create", help="create a new mapset")
     subparser.add_argument("path", help="path to the new mapset")
+    subparser.add_argument(
+        "--overwrite",
+        action="store_true",
+        help=_("overwrite an existing mapset"),
+    )
     subparser.set_defaults(func=subcommand_mapset_create)
 
     subparser = mapset_subparsers.add_parser("lock", help="lock a mapset")
@@ -133,9 +137,10 @@ def add_mapset_subparser(subparsers):
 
 
 def subcommand_mapset_create(args) -> int:
+    """Translates args to function parameters"""
     try:
-        create_mapset(args.path)
-    except (ScriptError, OSError) as error:
+        gs.create_mapset(args.path, overwrite=args.overwrite)
+    except (ValueError, OSError) as error:
         print(_("Error creating mapset: {}").format(error), file=sys.stderr)
         return 1
     return 0
diff --git a/python/grass/app/tests/grass_app_cli_test.py b/python/grass/app/tests/grass_app_cli_test.py
index 2c8c90a5cca..6cbf57779a6 100644
--- a/python/grass/app/tests/grass_app_cli_test.py
+++ b/python/grass/app/tests/grass_app_cli_test.py
@@ -240,13 +240,13 @@ def test_create_mapset(tmp_path):
 
 
 def test_mapset_create_exists(tmp_path):
-    """Check that creating mapset fails when mapset already exists"""
+    """Check that creating mapset fails unless --overwrite is used"""
     project = tmp_path / "test_1"
     mapset = project / "data_1"
     assert main(["project", "create", str(project)]) == 0
     assert main(["mapset", "create", str(mapset)]) == 0
     assert main(["mapset", "create", str(mapset)]) == 1
-    # There is no overwrite option for mapset yet, so we don't test that.
+    assert main(["mapset", "create", "--overwrite", str(mapset)]) == 0
 
 
 def test_create_overwrite(tmp_path):
diff --git a/python/grass/script/__init__.py b/python/grass/script/__init__.py
index 859c59550a3..3442c8130ca 100644
--- a/python/grass/script/__init__.py
+++ b/python/grass/script/__init__.py
@@ -8,6 +8,7 @@
     compare_key_value_text_files,
     create_environment,
     create_location,
+    create_mapset,
     create_project,
     debug,
     debug_level,
@@ -131,6 +132,7 @@
     "compare_key_value_text_files",
     "create_environment",
     "create_location",
+    "create_mapset",
     "create_project",
     "db_begin_transaction",
     "db_commit_transaction",
diff --git a/python/grass/script/core.py b/python/grass/script/core.py
index 389e7c2dd5b..bf7db9df3bf 100644
--- a/python/grass/script/core.py
+++ b/python/grass/script/core.py
@@ -2121,6 +2121,122 @@ def local_env():
         )
 
 
+def create_mapset(
+    path: str | os.PathLike | None = None,
+    /,
+    *,
+    name: str | None = None,
+    overwrite: bool = False,
+    initialize_db: bool = True,
+    env: _Env = None,
+) -> None:
+    """Create a new mapset in an existing project
+
+    The project must already exist. The new mapset uses the project's CRS
+    and its initial computational region is set from the project's default
+    region (defined in the PERMANENT mapset).
+
+    By default, the database connection is initialized (equivalent to
+    ``db.connect -c``), so the mapset is ready for use with vector attribute
+    data. Set *initialize_db* to False to skip this step.
+
+    The path can be provided in several ways:
+
+    * Full path to the new mapset in an existing project::
+
+          create_mapset("/home/user/grassdata/project/new_mapset")
+
+    * Path to an existing project with the mapset name as *name*::
+
+          create_mapset("/home/user/grassdata/project", name="new_mapset")
+
+    * Mapset name only, using the current session's project::
+
+          create_mapset(name="new_mapset")
+          create_mapset(name="new_mapset", env=session.env)
+
+    :param path: path to the new mapset or to the project if *name* is given;
+                 can be omitted when *name* is given and a session is active
+    :param name: mapset name to create (if not part of *path*)
+    :param overwrite: True to overwrite an existing mapset; the existing
+                      mapset and all its data will be deleted
+    :param initialize_db: True to initialize the default database
+                          connection in the new mapset (default True)
+    :param env: environment for the session; if not provided, ``os.environ``
+                is used
+
+    :raises ValueError: when neither *path* nor *name* is provided; when
+        *name* is given without *path* and no session is active; when the
+        mapset name is illegal or is ``PERMANENT``; when the project does
+        not exist; or when the mapset already exists and *overwrite* is
+        False
+    :raises OSError: when the underlying directory creation fails
+    """
+    from grass.grassdb.create import create_mapset as grassdb_create_mapset
+
+    if env is None:
+        env = os.environ
+
+    if path is not None and name:
+        path = Path(path) / name
+    elif path is None and name:
+        if not env.get("GISRC"):
+            msg = "No active session. Provide path or start a session first"
+            raise ValueError(msg)
+        gisenv_data = gisenv(env=env)
+        path = Path(gisenv_data["GISDBASE"]) / gisenv_data["LOCATION_NAME"] / name
+    elif path is None and not name:
+        msg = "Either path or name must be provided"
+        raise ValueError(msg)
+
+    mapset_path = resolve_mapset_path(path=path)
+
+    if not legal_name(mapset_path.mapset):
+        msg = f"Illegal mapset name <{mapset_path.mapset}>"
+        raise ValueError(msg)
+
+    if mapset_path.mapset == "PERMANENT":
+        msg = "Cannot create PERMANENT mapset (it is managed by the project)"
+        raise ValueError(msg)
+
+    project_dir = mapset_path.path.parent
+    if not project_dir.exists():
+        msg = (
+            f"Project <{mapset_path.location}> does not exist in "
+            f"<{mapset_path.directory}>"
+        )
+        raise ValueError(msg)
+
+    permanent_dir = project_dir / "PERMANENT"
+    if not permanent_dir.exists():
+        msg = (
+            f"Project <{mapset_path.location}> is not a valid project "
+            "(missing PERMANENT mapset)"
+        )
+        raise ValueError(msg)
+
+    if mapset_path.path.exists():
+        if not overwrite:
+            msg = (
+                f"Mapset <{mapset_path.mapset}> already exists in project "
+                f"<{mapset_path.location}>"
+            )
+            raise ValueError(msg)
+        shutil.rmtree(mapset_path.path)
+
+    grassdb_create_mapset(
+        mapset_path.directory, mapset_path.location, mapset_path.mapset
+    )
+
+    if initialize_db:
+        # Lazy import to avoid circular dependency between grass.script
+        # and grass.script.setup at module load time.
+        from grass.script import setup  # pylint: disable=import-outside-toplevel
+
+        with setup.init(mapset_path.path, env=env.copy()) as session:
+            run_command("db.connect", flags="c", env=session.env)
+
+
 def _set_location_description(path, location, text):
     """Set description (aka title aka MYNAME) for a location
 
diff --git a/python/grass/script/tests/grass_script_create_mapset_test.py b/python/grass/script/tests/grass_script_create_mapset_test.py
new file mode 100644
index 00000000000..9cc0c91b764
--- /dev/null
+++ b/python/grass/script/tests/grass_script_create_mapset_test.py
@@ -0,0 +1,186 @@
+"""Tests for grass.script.create_mapset"""
+
+import os
+
+import pytest
+
+import grass.script as gs
+from grass.tools import Tools
+
+
+@pytest.fixture
+def project_path(tmp_path):
+    """Create a XY project and return its path."""
+    project = tmp_path / "test_project"
+    gs.create_project(project)
+    return project
+
+
+def test_create_mapset_full_path(project_path):
+    """Check that mapset is created when full path is given."""
+    mapset_path = project_path / "new_mapset"
+    gs.create_mapset(mapset_path, initialize_db=False)
+    assert mapset_path.exists()
+    assert (mapset_path / "WIND").exists()
+
+
+def test_create_mapset_string_path(project_path):
+    """Check that mapset is created when path is given as a string."""
+    gs.create_mapset(str(project_path), name="new_mapset", initialize_db=False)
+    mapset_path = project_path / "new_mapset"
+    assert mapset_path.exists()
+    assert (mapset_path / "WIND").exists()
+
+
+def test_create_mapset_with_name(project_path):
+    """Check that mapset is created when project path and name are given."""
+    gs.create_mapset(project_path, name="new_mapset", initialize_db=False)
+    mapset_path = project_path / "new_mapset"
+    assert mapset_path.exists()
+    assert (mapset_path / "WIND").exists()
+
+
+def test_create_mapset_usable(project_path):
+    """Check that a created mapset can be used in a session."""
+    gs.create_mapset(project_path, name="new_mapset")
+    with gs.setup.init(project_path / "new_mapset", env=os.environ.copy()) as session:
+        info = gs.gisenv(env=session.env)
+        assert info["MAPSET"] == "new_mapset"
+
+
+def test_create_mapset_no_overwrite(project_path):
+    """Check that existing mapset raises error without overwrite."""
+    gs.create_mapset(project_path, name="new_mapset")
+    with pytest.raises(ValueError, match="already exists"):
+        gs.create_mapset(project_path, name="new_mapset")
+
+
+def test_create_mapset_overwrite(project_path):
+    """Check that existing mapset can be overwritten."""
+    mapset_path = project_path / "new_mapset"
+    gs.create_mapset(project_path, name="new_mapset", initialize_db=False)
+    # Add a file to verify old content is removed
+    marker = mapset_path / "marker_file"
+    marker.write_text("test")
+    assert marker.exists()
+
+    gs.create_mapset(
+        project_path, name="new_mapset", overwrite=True, initialize_db=False
+    )
+    assert mapset_path.exists()
+    assert (mapset_path / "WIND").exists()
+    assert not marker.exists()
+
+
+def test_create_mapset_nonexistent_project(tmp_path):
+    """Check error when project does not exist."""
+    with pytest.raises(ValueError, match="does not exist"):
+        gs.create_mapset(tmp_path / "nonexistent" / "new_mapset")
+
+
+def test_create_mapset_invalid_project(tmp_path):
+    """Check error when project directory exists but has no PERMANENT mapset."""
+    invalid_project = tmp_path / "invalid_project"
+    invalid_project.mkdir()
+    with pytest.raises(ValueError, match="PERMANENT"):
+        gs.create_mapset(invalid_project, name="new_mapset")
+
+
+def test_create_mapset_permanent_rejected(project_path):
+    """Check that creating PERMANENT mapset is rejected."""
+    with pytest.raises(ValueError, match="PERMANENT"):
+        gs.create_mapset(project_path, name="PERMANENT")
+
+
+@pytest.mark.parametrize("name", [".hidden", "has space", "with@at"])
+def test_create_mapset_illegal_name(project_path, name):
+    """Check that illegal mapset names are rejected."""
+    with pytest.raises(ValueError, match="Illegal"):
+        gs.create_mapset(project_path, name=name, initialize_db=False)
+
+
+def test_create_multiple_mapsets(project_path):
+    """Check that multiple mapsets can be created in the same project."""
+    names = ["mapset_a", "mapset_b", "mapset_c"]
+    for name in names:
+        gs.create_mapset(project_path, name=name, initialize_db=False)
+    for name in names:
+        assert (project_path / name).exists()
+        assert (project_path / name / "WIND").exists()
+
+
+def test_create_mapset_name_only(project_path):
+    """Check that mapset is created using only name within an active session."""
+    with gs.setup.init(project_path, env=os.environ.copy()) as session:
+        gs.create_mapset(name="new_mapset", env=session.env)
+    mapset_path = project_path / "new_mapset"
+    assert mapset_path.exists()
+    assert (mapset_path / "WIND").exists()
+
+
+@pytest.mark.usefixtures("mock_no_session")
+def test_create_mapset_name_only_no_session():
+    """Check that name-only fails without an active session."""
+    with pytest.raises(ValueError, match="No active session"):
+        gs.create_mapset(name="new_mapset")
+
+
+def test_create_mapset_no_arguments():
+    """Check that calling without path or name raises an error."""
+    with pytest.raises(ValueError, match="Either path or name"):
+        gs.create_mapset()
+
+
+def test_create_mapset_db_initialized(project_path):
+    """Check that database connection is initialized by default."""
+    gs.create_mapset(project_path, name="new_mapset")
+    mapset_path = project_path / "new_mapset"
+    assert (mapset_path / "VAR").exists()
+    with gs.setup.init(mapset_path, env=os.environ.copy()) as session:
+        tools = Tools(session=session)
+        conn = tools.db_connect(flags="p", format="json")
+        assert conn["driver"] == "sqlite"
+        assert "new_mapset" in conn["database"]
+
+
+def test_create_mapset_db_not_initialized(project_path):
+    """Check that database initialization is skipped when disabled."""
+    gs.create_mapset(project_path, name="new_mapset", initialize_db=False)
+    mapset_path = project_path / "new_mapset"
+    assert mapset_path.exists()
+    assert (mapset_path / "WIND").exists()
+    assert not (mapset_path / "VAR").exists()
+
+
+def test_create_mapset_with_existing_session_env(project_path):
+    """Check that creating a mapset works when env comes from an existing session.
+
+    The env already has a GISRC pointing to PERMANENT. The DB initialization
+    must create its own session for the new mapset, not reuse the old one.
+    """
+    with gs.setup.init(project_path, env=os.environ.copy()) as session:
+        gs.create_mapset(project_path, name="new_mapset", env=session.env)
+    mapset_path = project_path / "new_mapset"
+    assert mapset_path.exists()
+    assert (mapset_path / "WIND").exists()
+    assert (mapset_path / "VAR").exists()
+    with gs.setup.init(mapset_path, env=os.environ.copy()) as session:
+        tools = Tools(session=session)
+        conn = tools.db_connect(flags="p", format="json")
+        assert conn["driver"] == "sqlite"
+        assert "new_mapset" in conn["database"]
+
+
+def test_create_mapset_region_from_default(project_path):
+    """Check that the new mapset's region matches the project's default region."""
+    with gs.setup.init(project_path, env=os.environ.copy()) as session:
+        tools = Tools(session=session)
+        tools.g_region(n=100, s=0, e=200, w=0, res=10, flags="s")
+    gs.create_mapset(project_path, name="new_mapset")
+    with gs.setup.init(project_path / "new_mapset", env=os.environ.copy()) as session:
+        tools = Tools(session=session)
+        region = tools.g_region(flags="p", format="json")
+        assert region["north"] == 100
+        assert region["south"] == 0
+        assert region["east"] == 200
+        assert region["west"] == 0