diff --git a/mypy/checker.py b/mypy/checker.py
index 63e128f78310..163252829f94 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -5036,6 +5036,8 @@ def visit_if_stmt(self, s: IfStmt) -> None:
 
                 if_map, else_map = self.find_isinstance_check(e)
 
+                s.unreachable_else = else_map is None
+
                 # XXX Issue a warning if condition is always False?
                 with self.binder.frame_context(can_skip=True, fall_through=2):
                     self.push_type_map(if_map, from_assignment=False)
diff --git a/mypy/nodes.py b/mypy/nodes.py
index 040f3fc28dce..4cbd7fbb8fa2 100644
--- a/mypy/nodes.py
+++ b/mypy/nodes.py
@@ -1792,19 +1792,21 @@ def accept(self, visitor: StatementVisitor[T]) -> T:
 
 
 class IfStmt(Statement):
-    __slots__ = ("expr", "body", "else_body")
+    __slots__ = ("expr", "body", "else_body", "unreachable_else")
 
-    __match_args__ = ("expr", "body", "else_body")
+    __match_args__ = ("expr", "body", "else_body", "unreachable_else")
 
     expr: list[Expression]
     body: list[Block]
     else_body: Block | None
+    unreachable_else: bool
 
     def __init__(self, expr: list[Expression], body: list[Block], else_body: Block | None) -> None:
         super().__init__()
         self.expr = expr
         self.body = body
         self.else_body = else_body
+        self.unreachable_else = False
 
     def accept(self, visitor: StatementVisitor[T]) -> T:
         return visitor.visit_if_stmt(self)
diff --git a/mypy/partially_defined.py b/mypy/partially_defined.py
index 38154cf697e1..fad1f79493ad 100644
--- a/mypy/partially_defined.py
+++ b/mypy/partially_defined.py
@@ -395,11 +395,13 @@ def visit_if_stmt(self, o: IfStmt) -> None:
                 continue
             b.accept(self)
             self.tracker.next_branch()
-        if o.else_body:
-            if not o.else_body.is_unreachable:
-                o.else_body.accept(self)
-            else:
+        if o.unreachable_else:
+            self.tracker.skip_branch()
+        elif o.else_body:
+            if o.else_body.is_unreachable:
                 self.tracker.skip_branch()
+            else:
+                o.else_body.accept(self)
         self.tracker.end_branch_statement()
 
     def visit_match_stmt(self, o: MatchStmt) -> None:
diff --git a/test-data/unit/check-possibly-undefined.test b/test-data/unit/check-possibly-undefined.test
index ae277949c049..fb2edc39aa15 100644
--- a/test-data/unit/check-possibly-undefined.test
+++ b/test-data/unit/check-possibly-undefined.test
@@ -1043,3 +1043,27 @@ def foo(x: Union[int, str]) -> None:
         assert_never(x)
     f  # OK
 [builtins fixtures/tuple.pyi]
+
+[case testOmittedUnrequiredElse]
+# flags: --enable-error-code possibly-undefined
+from typing import Literal
+
+a: Literal[True]
+if a:
+    w = 1
+w + 1
+
+b: bool
+if b:
+    x = 1
+elif not b:
+    x = 2
+x + 1
+
+if b:
+    y = 1
+elif not b:
+    if a:
+        z = 2
+    y = z
+y + 1