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 (also known as directional or weathercock stability). It is part of the aircraft empennage, specifically of its stabilizers.
The vertical tail is typically mounted on top of the rear fuselage, with the horizontal stabilizers mounted on the side of the fuselage (a configuration termed "conventional tail"). Other configurations, such as T-tail or twin tail, are sometimes used instead.
Vertical stabilizers have occasionally been used in motor sports, with for example in Le Mans Prototype racing.