Military aircraft insignia are insignia applied to military aircraft to visually identify the nation or branch of military service to which the aircraft belong. Many insignia are in the form of a circular roundel or modified roundel; other shapes such as stars, crosses, squares, or triangles are also used. Insignia are often displayed on the sides of the fuselage, the upper and lower surfaces of the wings, as well as on the fin or rudder of an aircraft, although considerable variation can be found amongst different air arms and within specific air arms over time.

A roundel is a circular disc used as a symbol. The term is used in heraldry, but also commonly used to refer to a type of national insignia used on military aircraft, generally circular in shape and usually comprising concentric rings of different colours. Other symbols also often use round shapes.