diff --git a/pylint/checkers/python3.py b/pylint/checkers/python3.py
new file mode 100644
index 00000000000..f566b122719
--- /dev/null
+++ b/pylint/checkers/python3.py
@@ -0,0 +1,39 @@
+# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+# For details: https://github.com/PyCQA/pylint/blob/main/LICENSE
+
+"""This is the remnant of the python3 checker. It was removed because
+the transition from python 2 to python3 is behind us, but some checks
+are still useful in python3 after all.
+See https://github.com/PyCQA/pylint/issues/5025
+"""
+
+
+from pylint import checkers, interfaces
+from pylint.checkers import utils
+
+
+class Python3Checker(checkers.BaseChecker):
+
+    __implements__ = interfaces.IAstroidChecker
+    enabled = True
+    name = "python3"
+
+    msgs = {
+        "W1641": (
+            "Implementing __eq__ without also implementing __hash__",
+            "eq-without-hash",
+            "Used when a class implements __eq__ but not __hash__.  In Python 2, objects "
+            "get object.__hash__ as the default implementation, in Python 3 objects get "
+            "None as their default __hash__ implementation if they also implement __eq__.",
+        ),
+    }
+
+    @utils.check_messages("eq-without-hash")
+    def visit_classdef(self, node):
+        locals_and_methods = set(node.locals).union(x.name for x in node.mymethods())
+        if "__eq__" in locals_and_methods and "__hash__" not in locals_and_methods:
+            self.add_message("eq-without-hash", node=node)
+
+
+def register(linter):
+    linter.register_checker(Python3Checker(linter))
diff --git a/pylint/constants.py b/pylint/constants.py
index c3b94863dc5..eb0a6183ad6 100644
--- a/pylint/constants.py
+++ b/pylint/constants.py
@@ -80,8 +80,9 @@ class DeletedMessage(NamedTuple):
     old_names: List[Tuple[str, str]] = []
 
 
-DELETED_MSGID_PREFIXES = [
-    16,  # the PY3K+ checker, see https://github.com/PyCQA/pylint/pull/4942
+DELETED_MSGID_PREFIXES: List[int] = [
+    # The PY3K+ checker was deleted see https://github.com/PyCQA/pylint/pull/4942
+    # And then reinstated see https://github.com/PyCQA/pylint/issues/5025
 ]
 
 DELETED_MESSAGES = [
@@ -139,7 +140,6 @@ class DeletedMessage(NamedTuple):
     DeletedMessage("W1638", "range-builtin-not-iterating"),
     DeletedMessage("W1639", "filter-builtin-not-iterating"),
     DeletedMessage("W1640", "using-cmp-argument"),
-    DeletedMessage("W1641", "eq-without-hash"),
     DeletedMessage("W1642", "div-method"),
     DeletedMessage("W1643", "idiv-method"),
     DeletedMessage("W1644", "rdiv-method"),
diff --git a/tests/functional/a/access/access_to_protected_members.py b/tests/functional/a/access/access_to_protected_members.py
index 7d732dcc562..f5118b667b2 100644
--- a/tests/functional/a/access/access_to_protected_members.py
+++ b/tests/functional/a/access/access_to_protected_members.py
@@ -59,7 +59,7 @@ def incorrect_access(self):
         return None
 
 
-class Issue1802(object):
+class Issue1802(object): # [eq-without-hash]
     """Test for GitHub issue 1802"""
     def __init__(self, value):
         self._foo = value
diff --git a/tests/functional/a/access/access_to_protected_members.txt b/tests/functional/a/access/access_to_protected_members.txt
index d9dfd96ce11..ab00aea3a3e 100644
--- a/tests/functional/a/access/access_to_protected_members.txt
+++ b/tests/functional/a/access/access_to_protected_members.txt
@@ -4,6 +4,7 @@ protected-access:42:6:42:21::Access to a protected member _protected of a client
 protected-access:43:0:43:19::Access to a protected member _cls_protected of a client class:UNDEFINED
 protected-access:44:6:44:25::Access to a protected member _cls_protected of a client class:UNDEFINED
 protected-access:58:19:58:40:Issue1031.incorrect_access:Access to a protected member _protected of a client class:UNDEFINED
+eq-without-hash:62:0:101:20:Issue1802:Implementing __eq__ without also implementing __hash__:UNDEFINED
 protected-access:72:48:72:63:Issue1802.__eq__:Access to a protected member __private of a client class:UNDEFINED
 protected-access:80:32:80:42:Issue1802.not_in_special:Access to a protected member _foo of a client class:UNDEFINED
 protected-access:100:32:100:42:Issue1802.__fake_special__:Access to a protected member _foo of a client class:UNDEFINED
diff --git a/tests/functional/e/eq_without_hash.py b/tests/functional/e/eq_without_hash.py
new file mode 100644
index 00000000000..62682b01927
--- /dev/null
+++ b/tests/functional/e/eq_without_hash.py
@@ -0,0 +1,11 @@
+"""Regression test for #5025"""
+
+# pylint: disable=invalid-name,missing-docstring, too-few-public-methods
+
+
+class AClass:  # [eq-without-hash]
+    def __init__(self) -> None:
+        self.x = 5
+
+    def __eq__(self, other: object) -> bool:
+        return isinstance(other, AClass) and other.x == self.x
diff --git a/tests/functional/e/eq_without_hash.txt b/tests/functional/e/eq_without_hash.txt
new file mode 100644
index 00000000000..b56a1218ad8
--- /dev/null
+++ b/tests/functional/e/eq_without_hash.txt
@@ -0,0 +1 @@
+eq-without-hash:6:0:11:62:AClass:Implementing __eq__ without also implementing __hash__:UNDEFINED
diff --git a/tests/functional/m/missing/missing_function_docstring_rgx.py b/tests/functional/m/missing/missing_function_docstring_rgx.py
index 3c910d1a99b..56ab7cf4848 100644
--- a/tests/functional/m/missing/missing_function_docstring_rgx.py
+++ b/tests/functional/m/missing/missing_function_docstring_rgx.py
@@ -6,6 +6,6 @@ class MyClass:
     pass
 
 
-class Child(MyClass):
+class Child(MyClass):  # [eq-without-hash]
     def __eq__(self, other):  # [missing-function-docstring]
         return True
diff --git a/tests/functional/m/missing/missing_function_docstring_rgx.txt b/tests/functional/m/missing/missing_function_docstring_rgx.txt
index ee085ec067b..e0ee03af551 100644
--- a/tests/functional/m/missing/missing_function_docstring_rgx.txt
+++ b/tests/functional/m/missing/missing_function_docstring_rgx.txt
@@ -1 +1,2 @@
+eq-without-hash:9:0:11:19:Child:Implementing __eq__ without also implementing __hash__:UNDEFINED
 missing-function-docstring:10:4:11:19:Child.__eq__:Missing function or method docstring:INFERENCE
diff --git a/tests/functional/n/name/name_preset_snake_case.py b/tests/functional/n/name/name_preset_snake_case.py
index 75350497e4f..26e9dad5806 100644
--- a/tests/functional/n/name/name_preset_snake_case.py
+++ b/tests/functional/n/name/name_preset_snake_case.py
@@ -10,7 +10,7 @@ def say_hello(some_argument):
     return [some_argument * some_value for some_value in range(10)]
 
 
-class MyClass:  # [invalid-name]
+class MyClass:  # [invalid-name, eq-without-hash]]
     def __init__(self, arg_x):
         self._my_secret_x = arg_x
 
diff --git a/tests/functional/n/name/name_preset_snake_case.txt b/tests/functional/n/name/name_preset_snake_case.txt
index 664b2db90e9..2ae7b8744a6 100644
--- a/tests/functional/n/name/name_preset_snake_case.txt
+++ b/tests/functional/n/name/name_preset_snake_case.txt
@@ -1,4 +1,5 @@
 invalid-name:6:0:6:13::"Constant name ""SOME_CONSTANT"" doesn't conform to snake_case naming style ('([^\\W\\dA-Z][^\\WA-Z]*|__.*__)$' pattern)":HIGH
+eq-without-hash:13:0:22:83:MyClass:Implementing __eq__ without also implementing __hash__:UNDEFINED
 invalid-name:13:0:22:83:MyClass:"Class name ""MyClass"" doesn't conform to snake_case naming style ('[^\\W\\dA-Z][^\\WA-Z]+$' pattern)":HIGH
 invalid-name:25:0:26:8:sayHello:"Function name ""sayHello"" doesn't conform to snake_case naming style ('([^\\W\\dA-Z][^\\WA-Z]{2,}|_[^\\WA-Z]*|__[^\\WA-Z\\d_][^\\WA-Z]+__)$' pattern)":HIGH
 invalid-name:29:0:31:22:FooEnum:"Class name ""FooEnum"" doesn't conform to snake_case naming style ('[^\\W\\dA-Z][^\\WA-Z]+$' pattern)":HIGH
diff --git a/tests/functional/n/namePresetCamelCase.py b/tests/functional/n/namePresetCamelCase.py
index e048ec4d8a8..a442be76ca4 100644
--- a/tests/functional/n/namePresetCamelCase.py
+++ b/tests/functional/n/namePresetCamelCase.py
@@ -7,7 +7,7 @@ def sayHello(someArgument):
     return [someArgument * someValue for someValue in range(10)]
 
 
-class MyClass:  # [invalid-name]
+class MyClass:  # [invalid-name, eq-without-hash]
     def __init__(self, argX):
         self._mySecretX = argX
 
diff --git a/tests/functional/n/namePresetCamelCase.txt b/tests/functional/n/namePresetCamelCase.txt
index 7b9ec862317..bf4f7f52795 100644
--- a/tests/functional/n/namePresetCamelCase.txt
+++ b/tests/functional/n/namePresetCamelCase.txt
@@ -1,3 +1,4 @@
 invalid-name:3:0:3:13::"Constant name ""SOME_CONSTANT"" doesn't conform to camelCase naming style ('([^\\W\\dA-Z][^\\W_]*|__.*__)$' pattern)":HIGH
+eq-without-hash:10:0:19:79:MyClass:Implementing __eq__ without also implementing __hash__:UNDEFINED
 invalid-name:10:0:19:79:MyClass:"Class name ""MyClass"" doesn't conform to camelCase naming style ('[^\\W\\dA-Z][^\\W_]+$' pattern)":HIGH
 invalid-name:22:0:23:8:say_hello:"Function name ""say_hello"" doesn't conform to camelCase naming style ('([^\\W\\dA-Z][^\\W_]{2,}|__[^\\W\\dA-Z_]\\w+__)$' pattern)":HIGH
diff --git a/tests/functional/p/protected_access_special_methods_off.py b/tests/functional/p/protected_access_special_methods_off.py
index 8747b425e9d..714bcec5e3c 100644
--- a/tests/functional/p/protected_access_special_methods_off.py
+++ b/tests/functional/p/protected_access_special_methods_off.py
@@ -6,7 +6,7 @@
 # pylint: disable=too-few-public-methods
 
 
-class Protected:
+class Protected:  # [eq-without-hash]
     """A class"""
 
     def __init__(self):
diff --git a/tests/functional/p/protected_access_special_methods_off.txt b/tests/functional/p/protected_access_special_methods_off.txt
index ac9f6c66e3d..1f27d7a91c0 100644
--- a/tests/functional/p/protected_access_special_methods_off.txt
+++ b/tests/functional/p/protected_access_special_methods_off.txt
@@ -1,3 +1,4 @@
+eq-without-hash:9:0:23:40:Protected:Implementing __eq__ without also implementing __hash__:UNDEFINED
 unused-private-member:15:8:15:22:Protected.__init__:Unused private member `Protected.__private`:UNDEFINED
 protected-access:22:22:22:38:Protected._fake_special_:Access to a protected member _protected of a client class:UNDEFINED
 protected-access:23:25:23:40:Protected._fake_special_:Access to a protected member __private of a client class:UNDEFINED
diff --git a/tests/functional/p/protected_access_special_methods_on.py b/tests/functional/p/protected_access_special_methods_on.py
index 84488f44231..659fbe60270 100644
--- a/tests/functional/p/protected_access_special_methods_on.py
+++ b/tests/functional/p/protected_access_special_methods_on.py
@@ -6,7 +6,7 @@
 # pylint: disable=too-few-public-methods
 
 
-class Protected:
+class Protected:  # [eq-without-hash]
     """A class"""
 
     def __init__(self):
diff --git a/tests/functional/p/protected_access_special_methods_on.txt b/tests/functional/p/protected_access_special_methods_on.txt
index 0784dfbea6c..f7969457d58 100644
--- a/tests/functional/p/protected_access_special_methods_on.txt
+++ b/tests/functional/p/protected_access_special_methods_on.txt
@@ -1,3 +1,4 @@
+eq-without-hash:9:0:23:40:Protected:Implementing __eq__ without also implementing __hash__:UNDEFINED
 unused-private-member:15:8:15:22:Protected.__init__:Unused private member `Protected.__private`:UNDEFINED
 protected-access:18:26:18:42:Protected.__eq__:Access to a protected member _protected of a client class:UNDEFINED
 protected-access:22:22:22:38:Protected._fake_special_:Access to a protected member _protected of a client class:UNDEFINED