diff --git a/src/narwhals/_typing.py b/src/narwhals/_typing.py
index 8361d96303..189a1543b6 100644
--- a/src/narwhals/_typing.py
+++ b/src/narwhals/_typing.py
@@ -1,7 +1,18 @@
+"""Type aliases describing the backends Narwhals dispatches to.
+
+Built-in backends are enumerated as `Literal` unions (`Backend`, `EagerAllowed`, `LazyAllowed`, ...).
+Plugin backends are discovered at runtime and cannot join those unions, so `PluginName` uses a
+[`NewType`](https://typing.python.org/en/latest/spec/aliases.html#newtype) instead:
+type checkers treat it as a distinct subtype of `str`, therefore:
+
+- an arbitrary `str` is still rejected where a `backend` is expected, and
+- a value explicitly wrapped as `PluginName("...")` is accepted.
+"""
+
 from __future__ import annotations
 
 from types import ModuleType
-from typing import TYPE_CHECKING, Literal
+from typing import TYPE_CHECKING, Literal, NewType
 
 from narwhals._typing_compat import TypeVar
 from narwhals._utils import Implementation, _NoDefault
@@ -91,7 +102,17 @@
 - An Implementation, such as: `Implementation.DASK`, `Implementation.PYSPARK`, ...
 """
 
-BackendT = TypeVar("BackendT", bound=Backend)
+PluginName = NewType("PluginName", str)
+"""Name of a plugin's [entry point](https://packaging.python.org/en/latest/specifications/entry-points/).
+
+- Wrap an entry point name to pass it wherever a `backend` is expected, e.g. `PluginName("my-plugin")`.
+- Add it to a signature's `IntoBackend` parameter to advertise plugin support, e.g. `IntoBackend[EagerAllowed | PluginName]`.
+
+See the `narwhals.plugins` module for how plugin authors register entry points
+and the contract a wrapped name must satisfy.
+"""
+
+BackendT = TypeVar("BackendT", bound=Backend | PluginName)
 IntoBackend: TypeAlias = BackendT | ModuleType
 """Anything that can be converted into a [`narwhals.Implementation`][].
 
diff --git a/src/narwhals/_utils.py b/src/narwhals/_utils.py
index 4bb942f91a..d625613f66 100644
--- a/src/narwhals/_utils.py
+++ b/src/narwhals/_utils.py
@@ -100,6 +100,7 @@
     from narwhals._typing import (
         Backend,
         IntoBackend,
+        PluginName,
         _ArrowImpl,
         _CuDFImpl,
         _DaskImpl,
@@ -140,8 +141,6 @@
         _SliceNone,
     )
 
-    UnknownBackendName: TypeAlias = str
-
     FrameOrSeriesT = TypeVar(
         "FrameOrSeriesT", bound=LazyFrame[Any] | DataFrame[Any] | Series[Any]
     )
@@ -395,7 +394,7 @@ def from_string(cls: type[Self], backend_name: str) -> Implementation:
 
     @classmethod
     def from_backend(
-        cls: type[Self], backend: IntoBackend[Backend] | UnknownBackendName
+        cls: type[Self], backend: IntoBackend[Backend | PluginName]
     ) -> Implementation:
         """Instantiate from native namespace module, string, or Implementation.
 
diff --git a/src/narwhals/dataframe.py b/src/narwhals/dataframe.py
index 3c7fb9ea15..46fdad0050 100644
--- a/src/narwhals/dataframe.py
+++ b/src/narwhals/dataframe.py
@@ -72,7 +72,13 @@
     from narwhals._compliant.typing import CompliantExprAny
     from narwhals._expression_parsing import ExprMetadata
     from narwhals._translate import IntoArrowTable
-    from narwhals._typing import EagerAllowed, IntoBackend, LazyAllowed, Polars
+    from narwhals._typing import (
+        EagerAllowed,
+        IntoBackend,
+        LazyAllowed,
+        PluginName,
+        Polars,
+    )
     from narwhals.group_by import GroupBy, LazyGroupBy
     from narwhals.typing import (
         AsofJoinStrategy,
@@ -502,7 +508,10 @@ def __init__(self, df: Any, *, level: Literal["full", "lazy", "interchange"]) ->
 
     @classmethod
     def from_arrow(
-        cls, native_frame: IntoArrowTable, *, backend: IntoBackend[EagerAllowed]
+        cls,
+        native_frame: IntoArrowTable,
+        *,
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> DataFrame[Any]:
         """Construct a DataFrame from an object which supports the PyCapsule Interface.
 
@@ -559,7 +568,7 @@ def from_dict(
         data: Mapping[str, Any],
         schema: IntoSchema | Mapping[str, IntoDType | None] | None = None,
         *,
-        backend: IntoBackend[EagerAllowed] | None = None,
+        backend: IntoBackend[EagerAllowed | PluginName] | None = None,
     ) -> DataFrame[Any]:
         """Instantiate DataFrame from dictionary.
 
@@ -622,7 +631,7 @@ def from_dicts(
         data: Sequence[Mapping[str, Any]],
         schema: IntoSchema | Mapping[str, IntoDType | None] | None = None,
         *,
-        backend: IntoBackend[EagerAllowed],
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> DataFrame[Any]:
         """Instantiate DataFrame from a sequence of dictionaries representing rows.
 
@@ -696,7 +705,7 @@ def from_numpy(
         data: _2DArray,
         schema: IntoSchema | Sequence[str] | None = None,
         *,
-        backend: IntoBackend[EagerAllowed],
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> DataFrame[Any]:
         """Construct a DataFrame from a NumPy ndarray.
 
diff --git a/src/narwhals/functions.py b/src/narwhals/functions.py
index c528ebf60c..a576c6b33d 100644
--- a/src/narwhals/functions.py
+++ b/src/narwhals/functions.py
@@ -43,7 +43,7 @@
 
     from narwhals._native import NativeDataFrame, NativeLazyFrame, NativeSeries
     from narwhals._translate import IntoArrowTable
-    from narwhals._typing import Backend, EagerAllowed, IntoBackend
+    from narwhals._typing import Backend, EagerAllowed, IntoBackend, PluginName
     from narwhals.dataframe import DataFrame, LazyFrame
     from narwhals.series import Series
     from narwhals.typing import (
@@ -169,7 +169,7 @@ def new_series(
     values: Any,
     dtype: IntoDType | None = None,
     *,
-    backend: IntoBackend[EagerAllowed],
+    backend: IntoBackend[EagerAllowed | PluginName],
 ) -> Series[Any]:
     """Instantiate Narwhals Series from iterable (e.g. list or array).
 
@@ -211,7 +211,7 @@ def _new_series_impl(
     values: Any,
     dtype: IntoDType | None = None,
     *,
-    backend: IntoBackend[EagerAllowed],
+    backend: IntoBackend[EagerAllowed | PluginName],
 ) -> Series[Any]:
     implementation = Implementation.from_backend(backend)
     if is_eager_allowed(implementation):
@@ -241,7 +241,7 @@ def from_dict(
     data: Mapping[str, Any],
     schema: IntoSchema | Mapping[str, IntoDType | None] | None = None,
     *,
-    backend: IntoBackend[EagerAllowed] | None = None,
+    backend: IntoBackend[EagerAllowed | PluginName] | None = None,
     native_namespace: ModuleType | None = None,  # noqa: ARG001
 ) -> DataFrame[Any]:
     """Instantiate DataFrame from dictionary.
@@ -332,7 +332,7 @@ def from_dicts(
     data: Sequence[Mapping[str, Any]],
     schema: IntoSchema | Mapping[str, IntoDType | None] | None = None,
     *,
-    backend: IntoBackend[EagerAllowed],
+    backend: IntoBackend[EagerAllowed | PluginName],
 ) -> DataFrame[Any]:
     """Instantiate DataFrame from a sequence of dictionaries representing rows.
 
@@ -393,7 +393,7 @@ def from_numpy(
     data: _2DArray,
     schema: IntoSchema | Sequence[str] | None = None,
     *,
-    backend: IntoBackend[EagerAllowed],
+    backend: IntoBackend[EagerAllowed | PluginName],
 ) -> DataFrame[Any]:
     """Construct a DataFrame from a NumPy ndarray.
 
@@ -482,7 +482,7 @@ def _is_into_schema(obj: Any) -> TypeIs[_IntoSchema]:
 
 
 def from_arrow(
-    native_frame: IntoArrowTable, *, backend: IntoBackend[EagerAllowed]
+    native_frame: IntoArrowTable, *, backend: IntoBackend[EagerAllowed | PluginName]
 ) -> DataFrame[Any]:  # pragma: no cover
     """Construct a DataFrame from an object which supports the PyCapsule Interface.
 
@@ -652,7 +652,7 @@ def _validate_separator_pyarrow(separator: str, **kwargs: Any) -> Any:
 def read_csv(
     source: FileSource,
     *,
-    backend: IntoBackend[EagerAllowed],
+    backend: IntoBackend[EagerAllowed | PluginName],
     separator: str = ",",
     **kwargs: Any,
 ) -> DataFrame[Any]:
@@ -727,7 +727,7 @@ def read_csv(
 def scan_csv(
     source: FileSource,
     *,
-    backend: IntoBackend[Backend],
+    backend: IntoBackend[Backend | PluginName],
     separator: str = ",",
     **kwargs: Any,
 ) -> LazyFrame[Any]:
@@ -813,7 +813,7 @@ def scan_csv(
 
 
 def read_parquet(
-    source: FileSource, *, backend: IntoBackend[EagerAllowed], **kwargs: Any
+    source: FileSource, *, backend: IntoBackend[EagerAllowed | PluginName], **kwargs: Any
 ) -> DataFrame[Any]:
     """Read into a DataFrame from a parquet file.
 
@@ -886,7 +886,7 @@ def read_parquet(
 
 
 def scan_parquet(
-    source: FileSource, *, backend: IntoBackend[Backend], **kwargs: Any
+    source: FileSource, *, backend: IntoBackend[Backend | PluginName], **kwargs: Any
 ) -> LazyFrame[Any]:
     """Lazily read from a parquet file.
 
diff --git a/src/narwhals/plugins.py b/src/narwhals/plugins.py
index a247fc6b22..ae823eec59 100644
--- a/src/narwhals/plugins.py
+++ b/src/narwhals/plugins.py
@@ -1,3 +1,16 @@
+"""Runtime discovery of, and dispatch to, Narwhals plugin backends.
+
+A plugin backend registers an [entry point](https://packaging.python.org/en/latest/specifications/entry-points/)
+in the `narwhals.plugins` group. Plugins are discovered at runtime, so their names
+cannot be enumerated in the `Literal` unions that describe built-in backends.
+
+`PluginName` bridges that gap: a plugin's entry point name, wrapped as
+`PluginName("my-plugin")`, is accepted wherever a `backend` is expected.
+
+The contract for plugin authors is that the wrapped string **must** name an
+installed plugin's entry point in the `narwhals.plugins` group.
+"""
+
 from __future__ import annotations
 
 import sys
@@ -5,6 +18,7 @@
 from typing import TYPE_CHECKING, Any, Protocol
 
 from narwhals._compliant import CompliantNamespace
+from narwhals._typing import PluginName
 from narwhals._typing_compat import TypeVar
 
 if TYPE_CHECKING:
@@ -23,7 +37,7 @@
     from narwhals.utils import Version
 
 
-__all__ = ["Plugin", "from_native"]
+__all__ = ["Plugin", "PluginName", "from_native"]
 
 CompliantAny: TypeAlias = (
     "CompliantDataFrameAny | CompliantLazyFrameAny | CompliantSeriesAny"
diff --git a/src/narwhals/series.py b/src/narwhals/series.py
index c6f9d9ba5b..d0688cba41 100644
--- a/src/narwhals/series.py
+++ b/src/narwhals/series.py
@@ -45,7 +45,7 @@
     from typing_extensions import Self
 
     from narwhals._compliant import CompliantSeries
-    from narwhals._typing import EagerAllowed, IntoBackend, NoDefault
+    from narwhals._typing import EagerAllowed, IntoBackend, NoDefault, PluginName
     from narwhals.dataframe import DataFrame, MultiIndexSelector
     from narwhals.dtypes import DType
     from narwhals.typing import (
@@ -121,7 +121,7 @@ def from_numpy(
         values: _1DArray,
         dtype: IntoDType | None = None,
         *,
-        backend: IntoBackend[EagerAllowed],
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> Series[Any]:
         """Construct a Series from a NumPy ndarray.
 
@@ -186,7 +186,7 @@ def from_iterable(
         values: Iterable[Any],
         dtype: IntoDType | None = None,
         *,
-        backend: IntoBackend[EagerAllowed],
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> Series[Any]:
         """Construct a Series from an iterable.
 
diff --git a/src/narwhals/stable/v1/__init__.py b/src/narwhals/stable/v1/__init__.py
index a730b927c7..6b89027a1f 100644
--- a/src/narwhals/stable/v1/__init__.py
+++ b/src/narwhals/stable/v1/__init__.py
@@ -103,6 +103,7 @@
         IntoBackend,
         LazyAllowed,
         Pandas,
+        PluginName,
         Polars,
     )
     from narwhals.dataframe import MultiColSelector, MultiIndexSelector
@@ -138,7 +139,10 @@ def __init__(self, df: Any, *, level: Literal["full", "lazy", "interchange"]) ->
 
     @classmethod
     def from_arrow(
-        cls, native_frame: IntoArrowTable, *, backend: IntoBackend[EagerAllowed]
+        cls,
+        native_frame: IntoArrowTable,
+        *,
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> DataFrame[Any]:
         result = super().from_arrow(native_frame, backend=backend)
         return cast("DataFrame[Any]", result)
@@ -149,7 +153,7 @@ def from_dict(
         data: Mapping[str, Any],
         schema: IntoSchema | Mapping[str, IntoDType | None] | None = None,
         *,
-        backend: IntoBackend[EagerAllowed] | None = None,
+        backend: IntoBackend[EagerAllowed | PluginName] | None = None,
     ) -> DataFrame[Any]:
         result = super().from_dict(data, schema, backend=backend)
         return cast("DataFrame[Any]", result)
@@ -160,7 +164,7 @@ def from_dicts(
         data: Sequence[Any],
         schema: IntoSchema | Mapping[str, IntoDType | None] | None = None,
         *,
-        backend: IntoBackend[EagerAllowed],
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> DataFrame[Any]:
         result = super().from_dicts(data, schema, backend=backend)
         return cast("DataFrame[Any]", result)
@@ -171,7 +175,7 @@ def from_numpy(
         data: _2DArray,
         schema: IntoSchema | Sequence[str] | None = None,
         *,
-        backend: IntoBackend[EagerAllowed],
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> DataFrame[Any]:
         result = super().from_numpy(data, schema, backend=backend)
         return cast("DataFrame[Any]", result)
@@ -329,7 +333,7 @@ def from_numpy(
         values: _1DArray,
         dtype: IntoDType | None = None,
         *,
-        backend: IntoBackend[EagerAllowed],
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> Series[Any]:
         result = super().from_numpy(name, values, dtype, backend=backend)
         return cast("Series[Any]", result)
@@ -341,7 +345,7 @@ def from_iterable(
         values: Iterable[Any],
         dtype: IntoDType | None = None,
         *,
-        backend: IntoBackend[EagerAllowed],
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> Series[Any]:
         result = super().from_iterable(name, values, dtype, backend=backend)
         return cast("Series[Any]", result)
@@ -950,7 +954,7 @@ def new_series(
     values: Any,
     dtype: IntoDType | None = None,
     *,
-    backend: IntoBackend[EagerAllowed] | None = None,
+    backend: IntoBackend[EagerAllowed | PluginName] | None = None,
     native_namespace: ModuleType | None = None,  # noqa: ARG001
 ) -> Series[Any]:
     """Instantiate Narwhals Series from iterable (e.g. list or array).
@@ -959,7 +963,7 @@ def new_series(
     an is the same as `backend` but only accepts module types - for new code, we
     recommend using `backend`, as that's available beyond just `narwhals.stable.v1`.
     """
-    backend = cast("IntoBackend[EagerAllowed]", backend)
+    backend = cast("IntoBackend[EagerAllowed | PluginName]", backend)
     return _stableify(_new_series_impl(name, values, dtype, backend=backend))
 
 
@@ -967,7 +971,7 @@ def new_series(
 def from_arrow(
     native_frame: IntoArrowTable,
     *,
-    backend: IntoBackend[EagerAllowed] | None = None,
+    backend: IntoBackend[EagerAllowed | PluginName] | None = None,
     native_namespace: ModuleType | None = None,  # noqa: ARG001
 ) -> DataFrame[Any]:
     """Construct a DataFrame from an object which supports the PyCapsule Interface.
@@ -976,7 +980,7 @@ def from_arrow(
     an is the same as `backend` but only accepts module types - for new code, we
     recommend using `backend`, as that's available beyond just `narwhals.stable.v1`.
     """
-    backend = cast("IntoBackend[EagerAllowed]", backend)
+    backend = cast("IntoBackend[EagerAllowed | PluginName]", backend)
     return _stableify(nw_f.from_arrow(native_frame, backend=backend))
 
 
@@ -985,7 +989,7 @@ def from_dict(
     data: Mapping[str, Any],
     schema: IntoSchema | Mapping[str, IntoDType | None] | None = None,
     *,
-    backend: IntoBackend[EagerAllowed] | None = None,
+    backend: IntoBackend[EagerAllowed | PluginName] | None = None,
     native_namespace: ModuleType | None = None,  # noqa: ARG001
 ) -> DataFrame[Any]:
     """Instantiate DataFrame from dictionary.
@@ -1005,7 +1009,7 @@ def from_numpy(
     data: _2DArray,
     schema: IntoSchema | Sequence[str] | None = None,
     *,
-    backend: IntoBackend[EagerAllowed] | None = None,
+    backend: IntoBackend[EagerAllowed | PluginName] | None = None,
     native_namespace: ModuleType | None = None,  # noqa: ARG001
 ) -> DataFrame[Any]:
     """Construct a DataFrame from a NumPy ndarray.
@@ -1014,7 +1018,7 @@ def from_numpy(
     an is the same as `backend` but only accepts module types - for new code, we
     recommend using `backend`, as that's available beyond just `narwhals.stable.v1`.
     """
-    backend = cast("IntoBackend[EagerAllowed]", backend)
+    backend = cast("IntoBackend[EagerAllowed | PluginName]", backend)
     return _stableify(nw_f.from_numpy(data, schema, backend=backend))
 
 
@@ -1022,7 +1026,7 @@ def from_numpy(
 def read_csv(
     source: FileSource,
     *,
-    backend: IntoBackend[EagerAllowed] | None = None,
+    backend: IntoBackend[EagerAllowed | PluginName] | None = None,
     native_namespace: ModuleType | None = None,  # noqa: ARG001
     **kwargs: Any,
 ) -> DataFrame[Any]:
@@ -1032,7 +1036,7 @@ def read_csv(
     an is the same as `backend` but only accepts module types - for new code, we
     recommend using `backend`, as that's available beyond just `narwhals.stable.v1`.
     """
-    backend = cast("IntoBackend[EagerAllowed]", backend)
+    backend = cast("IntoBackend[EagerAllowed | PluginName]", backend)
     return _stableify(nw_f.read_csv(source, backend=backend, **kwargs))
 
 
@@ -1040,7 +1044,7 @@ def read_csv(
 def scan_csv(
     source: FileSource,
     *,
-    backend: IntoBackend[Backend] | None = None,
+    backend: IntoBackend[Backend | PluginName] | None = None,
     native_namespace: ModuleType | None = None,  # noqa: ARG001
     **kwargs: Any,
 ) -> LazyFrame[Any]:
@@ -1050,7 +1054,7 @@ def scan_csv(
     an is the same as `backend` but only accepts module types - for new code, we
     recommend using `backend`, as that's available beyond just `narwhals.stable.v1`.
     """
-    backend = cast("IntoBackend[Backend]", backend)
+    backend = cast("IntoBackend[Backend | PluginName]", backend)
     return _stableify(nw_f.scan_csv(source, backend=backend, **kwargs))
 
 
@@ -1058,7 +1062,7 @@ def scan_csv(
 def read_parquet(
     source: FileSource,
     *,
-    backend: IntoBackend[EagerAllowed] | None = None,
+    backend: IntoBackend[EagerAllowed | PluginName] | None = None,
     native_namespace: ModuleType | None = None,  # noqa: ARG001
     **kwargs: Any,
 ) -> DataFrame[Any]:
@@ -1068,7 +1072,7 @@ def read_parquet(
     an is the same as `backend` but only accepts module types - for new code, we
     recommend using `backend`, as that's available beyond just `narwhals.stable.v1`.
     """
-    backend = cast("IntoBackend[EagerAllowed]", backend)
+    backend = cast("IntoBackend[EagerAllowed | PluginName]", backend)
     return _stableify(nw_f.read_parquet(source, backend=backend, **kwargs))
 
 
@@ -1076,7 +1080,7 @@ def read_parquet(
 def scan_parquet(
     source: FileSource,
     *,
-    backend: IntoBackend[Backend] | None = None,
+    backend: IntoBackend[Backend | PluginName] | None = None,
     native_namespace: ModuleType | None = None,  # noqa: ARG001
     **kwargs: Any,
 ) -> LazyFrame[Any]:
@@ -1086,7 +1090,7 @@ def scan_parquet(
     an is the same as `backend` but only accepts module types - for new code, we
     recommend using `backend`, as that's available beyond just `narwhals.stable.v1`.
     """
-    backend = cast("IntoBackend[Backend]", backend)
+    backend = cast("IntoBackend[Backend | PluginName]", backend)
     return _stableify(nw_f.scan_parquet(source, backend=backend, **kwargs))
 
 
diff --git a/src/narwhals/stable/v2/__init__.py b/src/narwhals/stable/v2/__init__.py
index f45c1e2a1b..04ec4d6c36 100644
--- a/src/narwhals/stable/v2/__init__.py
+++ b/src/narwhals/stable/v2/__init__.py
@@ -92,6 +92,7 @@
         IntoBackend,
         LazyAllowed,
         Pandas,
+        PluginName,
         Polars,
     )
     from narwhals.dataframe import MultiColSelector, MultiIndexSelector
@@ -125,7 +126,10 @@ def __init__(self, df: Any, *, level: Literal["full", "lazy", "interchange"]) ->
 
     @classmethod
     def from_arrow(
-        cls, native_frame: IntoArrowTable, *, backend: IntoBackend[EagerAllowed]
+        cls,
+        native_frame: IntoArrowTable,
+        *,
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> DataFrame[Any]:
         result = super().from_arrow(native_frame, backend=backend)
         return cast("DataFrame[Any]", result)
@@ -136,7 +140,7 @@ def from_dict(
         data: Mapping[str, Any],
         schema: IntoSchema | Mapping[str, IntoDType | None] | None = None,
         *,
-        backend: IntoBackend[EagerAllowed] | None = None,
+        backend: IntoBackend[EagerAllowed | PluginName] | None = None,
     ) -> DataFrame[Any]:
         result = super().from_dict(data, schema, backend=backend)
         return cast("DataFrame[Any]", result)
@@ -147,7 +151,7 @@ def from_dicts(
         data: Sequence[Mapping[str, Any]],
         schema: IntoSchema | Mapping[str, IntoDType | None] | None = None,
         *,
-        backend: IntoBackend[EagerAllowed],
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> DataFrame[Any]:
         result = super().from_dicts(data, schema, backend=backend)
         return cast("DataFrame[Any]", result)
@@ -158,7 +162,7 @@ def from_numpy(
         data: _2DArray,
         schema: IntoSchema | Sequence[str] | None = None,
         *,
-        backend: IntoBackend[EagerAllowed],
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> DataFrame[Any]:
         result = super().from_numpy(data, schema, backend=backend)
         return cast("DataFrame[Any]", result)
@@ -282,7 +286,7 @@ def from_numpy(
         values: _1DArray,
         dtype: IntoDType | None = None,
         *,
-        backend: IntoBackend[EagerAllowed],
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> Series[Any]:
         result = super().from_numpy(name, values, dtype, backend=backend)
         return cast("Series[Any]", result)
@@ -294,7 +298,7 @@ def from_iterable(
         values: Iterable[Any],
         dtype: IntoDType | None = None,
         *,
-        backend: IntoBackend[EagerAllowed],
+        backend: IntoBackend[EagerAllowed | PluginName],
     ) -> Series[Any]:
         result = super().from_iterable(name, values, dtype, backend=backend)
         return cast("Series[Any]", result)
@@ -927,7 +931,7 @@ def new_series(
     values: Any,
     dtype: IntoDType | None = None,
     *,
-    backend: IntoBackend[EagerAllowed],
+    backend: IntoBackend[EagerAllowed | PluginName],
 ) -> Series[Any]:
     """Instantiate Narwhals Series from iterable (e.g. list or array).
 
@@ -949,7 +953,7 @@ def new_series(
 
 
 def from_arrow(
-    native_frame: IntoArrowTable, *, backend: IntoBackend[EagerAllowed]
+    native_frame: IntoArrowTable, *, backend: IntoBackend[EagerAllowed | PluginName]
 ) -> DataFrame[Any]:
     """Construct a DataFrame from an object which supports the PyCapsule Interface.
 
@@ -971,7 +975,7 @@ def from_dict(
     data: Mapping[str, Any],
     schema: IntoSchema | Mapping[str, IntoDType | None] | None = None,
     *,
-    backend: IntoBackend[EagerAllowed] | None = None,
+    backend: IntoBackend[EagerAllowed | PluginName] | None = None,
 ) -> DataFrame[Any]:
     """Instantiate DataFrame from dictionary.
 
@@ -1009,7 +1013,7 @@ def from_numpy(
     data: _2DArray,
     schema: IntoSchema | Sequence[str] | None = None,
     *,
-    backend: IntoBackend[EagerAllowed],
+    backend: IntoBackend[EagerAllowed | PluginName],
 ) -> DataFrame[Any]:
     """Construct a DataFrame from a NumPy ndarray.
 
@@ -1038,7 +1042,7 @@ def from_numpy(
 def read_csv(
     source: str,
     *,
-    backend: IntoBackend[EagerAllowed],
+    backend: IntoBackend[EagerAllowed | PluginName],
     separator: str = ",",
     **kwargs: Any,
 ) -> DataFrame[Any]:
@@ -1064,7 +1068,11 @@ def read_csv(
 
 
 def scan_csv(
-    source: str, *, backend: IntoBackend[Backend], separator: str = ",", **kwargs: Any
+    source: str,
+    *,
+    backend: IntoBackend[Backend | PluginName],
+    separator: str = ",",
+    **kwargs: Any,
 ) -> LazyFrame[Any]:
     """Lazily read from a CSV file.
 
@@ -1091,7 +1099,7 @@ def scan_csv(
 
 
 def read_parquet(
-    source: str, *, backend: IntoBackend[EagerAllowed], **kwargs: Any
+    source: str, *, backend: IntoBackend[EagerAllowed | PluginName], **kwargs: Any
 ) -> DataFrame[Any]:
     """Read into a DataFrame from a parquet file.
 
@@ -1112,7 +1120,7 @@ def read_parquet(
 
 
 def scan_parquet(
-    source: str, *, backend: IntoBackend[Backend], **kwargs: Any
+    source: str, *, backend: IntoBackend[Backend | PluginName], **kwargs: Any
 ) -> LazyFrame[Any]:
     """Lazily read from a parquet file.
 
diff --git a/tests/plugins_test.py b/tests/plugins_test.py
index 6de21e53f1..11bcd813e3 100644
--- a/tests/plugins_test.py
+++ b/tests/plugins_test.py
@@ -8,10 +8,12 @@
 import narwhals.stable.v1.dependencies as nw_v1_dependencies
 import narwhals.stable.v2.dependencies as nw_v2_dependencies
 from narwhals import dependencies as nw_dependencies
+from narwhals.plugins import PluginName
 
 if TYPE_CHECKING:
     from typing_extensions import Self
 
+    from narwhals._typing import EagerAllowed, IntoBackend
     from narwhals.plugins import Plugin
     from narwhals.utils import Version
 
@@ -132,3 +134,43 @@ def test_typing() -> None:
     import test_plugin
 
     _plugin: Plugin = test_plugin
+
+
+def test_plugin_name_runtime() -> None:
+    # `PluginName` is a `NewType`: identity at runtime, nominal for type checkers.
+    name = PluginName("some-plugin")
+    assert name == "some-plugin"
+    assert nw.Implementation.from_backend(name) is nw.Implementation.UNKNOWN
+
+
+if TYPE_CHECKING:
+    # Static-only regression guards for `PluginName`
+    def typing_backend_plugin_name(
+        plugin_name: PluginName,
+        dynamic_string: str,
+        eager_or_plugin: IntoBackend[EagerAllowed | PluginName],
+        df: nw.DataFrame[Any],
+    ) -> None:
+        data = {"a": [1, 2]}
+
+        # Accepted: an explicitly wrapped plugin name, everything `IntoBackend[EagerAllowed | PluginName]` covers.
+        nw.from_dict(data, backend=plugin_name)
+        nw.from_dict(data, backend=eager_or_plugin)
+        nw.new_series("a", [1, 2], backend=plugin_name)
+        nw.scan_csv("file.csv", backend=plugin_name)
+        nw.DataFrame.from_dict(data, backend=plugin_name)
+        nw.Implementation.from_backend(plugin_name)
+
+        # Rejected: opaque strings do not satisfy `PluginName`.
+        nw.from_dict(data, backend=dynamic_string)  # type: ignore[arg-type]
+        nw.new_series("a", [1, 2], backend=dynamic_string)  # type: ignore[arg-type]
+        nw.Implementation.from_backend(dynamic_string)  # type: ignore[arg-type]
+
+        # Rejected: lazy-only literals on eager constructors (no regression).
+        nw.from_dict(data, backend="duckdb")  # type: ignore[arg-type]
+
+        # Rejected: `.lazy` does not dispatch to plugins (yet).
+        df.lazy(plugin_name)  # type: ignore[arg-type]
+        lf = df.lazy()
+        # Rejected: `.collect` does not dispatch to plugins (yet).
+        lf.collect(plugin_name)  # type: ignore[arg-type]