diff --git a/amaranth/vendor/gowin.py b/amaranth/vendor/gowin.py
deleted file mode 100644
index fcf0df49b..000000000
--- a/amaranth/vendor/gowin.py
+++ /dev/null
@@ -1,16 +0,0 @@
-# TODO(amaranth-0.5): remove module
-
-import warnings
-import importlib
-from .. import vendor
-
-
-__all__ = ["GowinPlatform"]
-
-
-def __getattr__(name):
-    if name in __all__:
-        warnings.warn(f"instead of `{__name__}.{name}`, use `amaranth.vendor.{name}",
-                      DeprecationWarning, stacklevel=2)
-        return getattr(vendor, name)
-    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/amaranth/vendor/intel.py b/amaranth/vendor/intel.py
deleted file mode 100644
index 5788fe108..000000000
--- a/amaranth/vendor/intel.py
+++ /dev/null
@@ -1,16 +0,0 @@
-# TODO(amaranth-0.5): remove module
-
-import warnings
-import importlib
-from .. import vendor
-
-
-__all__ = ["IntelPlatform"]
-
-
-def __getattr__(name):
-    if name in __all__:
-        warnings.warn(f"instead of `{__name__}.{name}`, use `amaranth.vendor.{name}",
-                      DeprecationWarning, stacklevel=2)
-        return getattr(vendor, name)
-    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/amaranth/vendor/lattice_ecp5.py b/amaranth/vendor/lattice_ecp5.py
deleted file mode 100644
index 4dbd8b475..000000000
--- a/amaranth/vendor/lattice_ecp5.py
+++ /dev/null
@@ -1,16 +0,0 @@
-# TODO(amaranth-0.5): remove module
-
-import warnings
-import importlib
-from .. import vendor
-
-
-__all__ = ["LatticeECP5Platform"]
-
-
-def __getattr__(name):
-    if name in __all__:
-        warnings.warn(f"instead of `{__name__}.{name}`, use `amaranth.vendor.{name}",
-                      DeprecationWarning, stacklevel=2)
-        return getattr(vendor, name)
-    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/amaranth/vendor/lattice_ice40.py b/amaranth/vendor/lattice_ice40.py
deleted file mode 100644
index 06a12ab4a..000000000
--- a/amaranth/vendor/lattice_ice40.py
+++ /dev/null
@@ -1,16 +0,0 @@
-# TODO(amaranth-0.5): remove module
-
-import warnings
-import importlib
-from .. import vendor
-
-
-__all__ = ["LatticeICE40Platform"]
-
-
-def __getattr__(name):
-    if name in __all__:
-        warnings.warn(f"instead of `{__name__}.{name}`, use `amaranth.vendor.{name}",
-                      DeprecationWarning, stacklevel=2)
-        return getattr(vendor, name)
-    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/amaranth/vendor/lattice_machxo_2_3l.py b/amaranth/vendor/lattice_machxo_2_3l.py
deleted file mode 100644
index 1ac5a43a2..000000000
--- a/amaranth/vendor/lattice_machxo_2_3l.py
+++ /dev/null
@@ -1,16 +0,0 @@
-# TODO(amaranth-0.5): remove module
-
-import warnings
-import importlib
-from .. import vendor
-
-
-__all__ = ["LatticeMachXO2Platform", "LatticeMachXO3LPlatform"]
-
-
-def __getattr__(name):
-    if name in __all__:
-        warnings.warn(f"instead of `{__name__}.{name}`, use `amaranth.vendor.{name}",
-                      DeprecationWarning, stacklevel=2)
-        return getattr(vendor, name)
-    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/amaranth/vendor/quicklogic.py b/amaranth/vendor/quicklogic.py
deleted file mode 100644
index 8de7d2bf2..000000000
--- a/amaranth/vendor/quicklogic.py
+++ /dev/null
@@ -1,16 +0,0 @@
-# TODO(amaranth-0.5): remove module
-
-import warnings
-import importlib
-from .. import vendor
-
-
-__all__ = ["QuicklogicPlatform"]
-
-
-def __getattr__(name):
-    if name in __all__:
-        warnings.warn(f"instead of `{__name__}.{name}`, use `amaranth.vendor.{name}",
-                      DeprecationWarning, stacklevel=2)
-        return getattr(vendor, name)
-    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/amaranth/vendor/xilinx.py b/amaranth/vendor/xilinx.py
deleted file mode 100644
index 6862ca5f4..000000000
--- a/amaranth/vendor/xilinx.py
+++ /dev/null
@@ -1,16 +0,0 @@
-# TODO(amaranth-0.5): remove module
-
-import warnings
-import importlib
-from .. import vendor
-
-
-__all__ = ["XilinxPlatform"]
-
-
-def __getattr__(name):
-    if name in __all__:
-        warnings.warn(f"instead of `{__name__}.{name}`, use `amaranth.vendor.{name}",
-                      DeprecationWarning, stacklevel=2)
-        return getattr(vendor, name)
-    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
diff --git a/docs/changes.rst b/docs/changes.rst
index 93716d771..e205c2dda 100644
--- a/docs/changes.rst
+++ b/docs/changes.rst
@@ -23,6 +23,14 @@ Standard library changes
 * Removed: (deprecated in 0.4) :mod:`amaranth.lib.scheduler`. (`RFC 19`_)
 
 
+Platform integration changes
+----------------------------
+
+.. currentmodule:: amaranth.vendor
+
+* Removed: (deprecated in 0.4) :mod:`vendor.intel`, :mod:`vendor.lattice_ecp5`, :mod:`vendor.lattice_ice40`, :mod:`vendor.lattice_machxo2_3l`, :mod:`vendor.quicklogic`, :mod:`vendor.xilinx`. (`RFC 18`_)
+
+
 Version 0.4
 ===========