diff --git a/mypy/checker.py b/mypy/checker.py
index d94ab42c8479..a76bd0dce9d3 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -1790,11 +1790,59 @@ def visit_class_def(self, defn: ClassDef) -> None:
                     sig, _ = self.expr_checker.check_call(dec, [temp],
                                                           [nodes.ARG_POS], defn,
                                                           callable_name=fullname)
+
+                    if defn.info.is_enum and refers_to_fullname(decorator, 'enum.unique'):
+                        self.check_enum_unique_decorator(defn, decorator)
                 # TODO: Apply the sig to the actual TypeInfo so we can handle decorators
                 # that completely swap out the type.  (e.g. Callable[[Type[A]], Type[B]])
         if typ.is_protocol and typ.defn.type_vars:
             self.check_protocol_variance(defn)
 
+    def check_enum_unique_decorator(self, defn: ClassDef, decorator: Expression) -> None:
+        # TODO: this can also check known `Literal` types in the future.
+        known_values = []
+
+        # All `Enum`s are just a series of `a = 1`, `b = 2` assignments in their bodies.
+        # We need raw exressions in these assignments.
+        for node in defn.defs.body:
+            if not isinstance(node, AssignmentStmt):
+                continue
+
+            # Next, we need to be sure that all parts of `Enum` definition
+            # are just simple names and are present in `TypeInfo`.
+            for lvalue in node.lvalues:
+                if not isinstance(lvalue, NameExpr):
+                    continue
+                field = defn.info.get(lvalue.name)
+                if field is None or not isinstance(field.node, Var):
+                    continue
+
+                # Validation passed, continue.
+                is_known, value = mypy.checkexpr.try_getting_statically_known_value(
+                    node.rvalue)
+                if not is_known:
+                    # We continue, because value was not known.
+                    # But, others possibly still can be reported.
+                    continue
+                known_values.append(value)
+
+        # Since we might end up with unhashable objects, like `[1]` or `{}`,
+        # we cannot use `dict` or `Counter`.
+        # It should not hit us hard, because `Enum`s rarely have lots of values.
+        errors = []
+        seen = []
+        for value in known_values:
+            if value in seen:
+                errors.append(value)
+            if value not in seen:
+                seen.append(value)
+
+        # Now, report all errors:
+        for error in errors:
+            self.fail('Duplicate value "{}" in "{}" unique enum definition'.format(
+                error, defn.name,
+            ), defn)
+
     def check_final_deletable(self, typ: TypeInfo) -> None:
         # These checks are only for mypyc. Only perform some checks that are easier
         # to implement here than in mypyc.
diff --git a/mypy/checkexpr.py b/mypy/checkexpr.py
index b6dec2834449..1a85db51082e 100644
--- a/mypy/checkexpr.py
+++ b/mypy/checkexpr.py
@@ -5,7 +5,8 @@
 from contextlib import contextmanager
 import itertools
 from typing import (
-    Any, cast, Dict, Set, List, Tuple, Callable, Union, Optional, Sequence, Iterator
+    Any, cast, Dict, Set, List, Tuple, Callable, Union,
+    Optional, Sequence, Iterator, Iterable
 )
 from typing_extensions import ClassVar, Final, overload, TypeAlias as _TypeAlias
 
@@ -4578,3 +4579,77 @@ def get_partial_instance_type(t: Optional[Type]) -> Optional[PartialType]:
     if t is None or not isinstance(t, PartialType) or t.type is None:
         return None
     return t
+
+
+def try_getting_statically_known_value(node: Expression) -> Tuple[bool, Any]:
+    """We try to get statically known expression's value.
+
+    Imagine, that you have:
+
+       class Some(enum.Enum):
+           one = 'one'
+           two = ('t', 'w', 'o')
+           three = None
+           four = method_call()
+
+    The first boolean represent whether given node was a literal value.
+    The second element is literal's value if any.
+
+    When trying to call ``try_getting_literal_expr`` on ``Some.one``
+    it will return ``True, 'one'`` tuple.
+    On ``Some.two`` it will return ``True, ('t', 'w', 'o')`` tuple.
+    On ``three`` it will return ``True, None``.
+    On ``four`` it will return ``False, None``.
+
+    We also recurse into nested nodes like ``TupleExpr``, ``ListExpr``, etc.
+    """
+    if isinstance(node, (StrExpr, UnicodeExpr, IntExpr, FloatExpr, ComplexExpr)):
+        return True, node.value
+    if isinstance(node, BytesExpr):
+        # Since `bytes`'s value is store as `str` in `mypy`,
+        # we use this hack to tell them appart.
+        return True, f'b"{node.value}"'
+    if isinstance(node, NameExpr):
+        if node.name == 'None':
+            return True, None
+        if node.name in ('True', 'False'):
+            return True, node.name == 'True'
+    if isinstance(node, EllipsisExpr):
+        return True, ...
+
+    # Recursive types:
+    if isinstance(node, TupleExpr):
+        return _recursive_statically_known_value(node.items, tuple)
+    if isinstance(node, ListExpr):
+        return _recursive_statically_known_value(node.items, list)
+    if isinstance(node, SetExpr):
+        return _recursive_statically_known_value(node.items, set)
+    if isinstance(node, DictExpr):
+        keys = []
+        values = []
+        for key, value in node.items:
+            if key is None:
+                return False, None  # We've met `**` unpacking
+
+            known_key, key_value = try_getting_statically_known_value(key)
+            if not known_key:
+                return False, None
+            known_value, value_value = try_getting_statically_known_value(value)
+            if not known_value:
+                return False, None
+            keys.append(key_value)
+            values.append(value_value)
+        return True, dict(zip(keys, values))
+    return False, None
+
+
+def _recursive_statically_known_value(items: Iterable[Expression],
+                                      typ: type) -> Tuple[bool, Any]:
+    res: List[Any] = []
+    for item in items:
+        is_known, item_value = try_getting_statically_known_value(item)
+        if is_known:
+            res.append(item_value)
+        else:
+            return False, None
+    return True, typ(res)
diff --git a/test-data/unit/check-enum.test b/test-data/unit/check-enum.test
index 22d167f3487b..1d564c1c71ec 100644
--- a/test-data/unit/check-enum.test
+++ b/test-data/unit/check-enum.test
@@ -134,10 +134,11 @@ import enum
 @enum.unique
 class E(enum.Enum):
     x = 1
-    y = 1  # NOTE: This duplicate value is not detected by mypy at the moment
+    y = 1
 x = 1
 x = E.x
 [out]
+main:3: error: Duplicate value "1" in "E" unique enum definition
 main:7: error: Incompatible types in assignment (expression has type "E", variable has type "int")
 
 [case testIntEnum_assignToIntVariable]
@@ -1644,3 +1645,219 @@ class A(Enum):
     class Inner: pass
 class B(A): pass  # E: Cannot inherit from final class "A"
 [builtins fixtures/bool.pyi]
+
+
+[case testUniqueEnumCorrectStaticValues]
+from enum import Enum, IntEnum, Flag, IntFlag, unique
+
+@unique
+class EmptyEnum(Enum):
+    pass
+@unique
+class EmptyIntEnum(IntEnum):
+    pass
+@unique
+class EmptyFlag(Flag):
+    pass
+@unique
+class EmptyIntFlag(IntFlag):
+    pass
+
+@unique
+class NonEmptyEnum(Enum):
+    x = [1, 'a', (1, [1, 2])]
+    y = 2
+    z = '1'
+    n = None
+    a = (1,)
+    b = [1]
+    c = {1: 1}
+    d = {1}
+    e = ...
+    f = False
+    g = True
+    h = 1.5
+    j = 1j
+    k = b'1'
+@unique
+class NonEmptyIntEnum(IntEnum):
+    x = 1
+    y = 2
+@unique
+class NonEmptyFlag(Flag):
+    x = 'x'
+    y = 'y'
+@unique
+class NonEmptyIntFlag(IntFlag):
+    x = 1
+    y = 2
+[builtins fixtures/dict.pyi]
+
+[case testNonEnumUnique]
+from enum import unique
+@unique
+class A:
+    x = 1
+    y = 1
+[builtins fixtures/bool.pyi]
+
+[case testEnumNonUniqueDecorator]
+from enum import Enum
+def dec(t):
+    return t
+@dec
+class A(Enum):
+    x = 1
+    y = 1
+[builtins fixtures/bool.pyi]
+
+[case testEnumMetaUnique]
+from enum import unique, EnumMeta
+@unique
+class A(EnumMeta):
+    x = 1
+    y = 1
+[builtins fixtures/bool.pyi]
+
+[case testEnumDynamicValues]
+from typing import List
+from enum import Enum, unique
+
+# We cannot infer these yet (possibly - never):
+def y() -> int:
+    return 1
+z = [1]
+
+@unique
+class EmptyEnum(Enum):
+    a = z
+    b = z
+    c = y()
+    d = y()
+    e = z[0]
+    f = z[0]
+
+@unique
+class ComplexValuesEnum(Enum):
+    a = (z, z)
+    b = (z, z)
+    c = {y()}
+    d = {y()}
+    e = [z, y()]
+    f = [z, y()]
+    d1 = {z: 1}
+    d2 = {z: 1}
+    d3 = {1: y()}
+    d4 = {1: y()}
+    d5 = {z: y()}
+    d6 = {z: y()}
+
+@unique
+class EmptyIntEnum(Enum):  # E: Duplicate value "0" in "EmptyIntEnum" unique enum definition
+    a = z[0]
+    # This still raises, we know `1` is duplicated:
+    b = 0
+    c = 0
+    # This won't:
+    d = int()
+    e = int()
+[builtins fixtures/dict.pyi]
+
+[case testEnumUniqueSeveralLValues]
+from enum import Enum, unique
+@unique
+class IntFloatEnum(Enum):  # E: Duplicate value "1" in "IntFloatEnum" unique enum definition
+    x = y = 1
+[builtins fixtures/bool.pyi]
+
+[case testEnumUniqueUnpacking]
+from enum import Enum, unique
+@unique
+class UniqueEnum(Enum):
+    x, y = (1, 2)
+# TODO: should raise, but does not
+# TODO: this should be handled with `Literal` types
+@unique
+class NonUniqueEnum(Enum):
+    x, y = (1, 1)
+[builtins fixtures/bool.pyi]
+
+[case testEnumDuplocateStaticValues]
+from enum import Enum, unique
+
+@unique
+class IntFloatEnum(Enum):
+    x = 1
+    y = 1.0
+@unique
+class IntEnum(Enum):
+    x = 1
+    y = 1
+@unique
+class FloatEnum(Enum):
+    x = 1.0
+    y = 1.0
+@unique
+class ComplexEnum(Enum):
+    x = 1j
+    y = 1j
+@unique
+class StrEnum(Enum):
+    a = 'a'
+    b = 'a'
+@unique
+class BytesEnum(Enum):
+    a = b'a'
+    b = b'a'
+@unique
+class BytesStrEnum(Enum):
+    a = 'a'  # ok
+    b = b'a'
+@unique
+class BoolEnum(Enum):
+    a = True
+    b = True
+@unique
+class BoolIntEnum(Enum):
+    a = True
+    b = 1
+@unique
+class NoneEnum(Enum):
+    a = None
+    b = None
+@unique
+class ElipsisEnum(Enum):
+    a = ...
+    b = ...
+@unique
+class TupleEnum(Enum):
+    a = (True, 1, None)
+    b = (True, 1, None)
+@unique
+class ListEnum(Enum):
+    a = [1, (2, 3), [4, 5]]
+    b = [1, (2, 3), [4, 5]]
+@unique
+class SetEnum(Enum):
+    a = {1, True, 1.0}
+    b = {1}
+@unique
+class DictEnum(Enum):
+    a = {1: 'a'}
+    b = {1: 'a'}
+[out]
+main:4: error: Duplicate value "1.0" in "IntFloatEnum" unique enum definition
+main:8: error: Duplicate value "1" in "IntEnum" unique enum definition
+main:12: error: Duplicate value "1.0" in "FloatEnum" unique enum definition
+main:16: error: Duplicate value "1j" in "ComplexEnum" unique enum definition
+main:20: error: Duplicate value "a" in "StrEnum" unique enum definition
+main:24: error: Duplicate value "b"a"" in "BytesEnum" unique enum definition
+main:32: error: Duplicate value "True" in "BoolEnum" unique enum definition
+main:36: error: Duplicate value "1" in "BoolIntEnum" unique enum definition
+main:40: error: Duplicate value "None" in "NoneEnum" unique enum definition
+main:44: error: Duplicate value "Ellipsis" in "ElipsisEnum" unique enum definition
+main:48: error: Duplicate value "(True, 1, None)" in "TupleEnum" unique enum definition
+main:52: error: Duplicate value "[1, (2, 3), [4, 5]]" in "ListEnum" unique enum definition
+main:56: error: Duplicate value "{1}" in "SetEnum" unique enum definition
+main:60: error: Duplicate value "{1: 'a'}" in "DictEnum" unique enum definition
+[builtins fixtures/dict.pyi]
diff --git a/test-data/unit/fixtures/dict.pyi b/test-data/unit/fixtures/dict.pyi
index fd509de8a6c2..e7576c2cdd3b 100644
--- a/test-data/unit/fixtures/dict.pyi
+++ b/test-data/unit/fixtures/dict.pyi
@@ -46,6 +46,7 @@ class list(Sequence[T]): # needed by some test cases
     def append(self, item: T) -> None: pass
 
 class tuple(Generic[T]): pass
+class set(): pass
 class function: pass
 class float: pass
 class complex: pass