A twin tail is a type of vertical stabilizer arrangement found on the empennage of some aircraft. Two vertical stabilizers—often smaller on their own than a single conventional tail would be—are mounted at the outside of the aircraft's horizontal stabilizer. This arrangement is also known as an H-tail, as it resembles a capital "H" when viewed from the rear. The twin tail was used on a wide variety of World War II multi-engine designs that saw mass production, especially on the American B-24 Liberator and B-25 Mitchell bombers, the British Avro Lancaster and Handley Page Halifax heavy bombers, and the Soviet Union's Petlyakov Pe-2 attack bomber.

A vertical stabilizer or tail fin is the static part of the vertical tail of an aircraft. The term is commonly applied to the assembly of both this fixed surface and one or more movable rudders hinged to it. Their role is to provide control, stability and trim in yaw. It is part of the aircraft empennage, specifically of its stabilizers.