The square-tailed nightjar (Caprimulgus fossii) is a species of nightjar in the family Caprimulgidae which is native to tropical and subtropical woodlands of the Afrotropics. It has an extensive range south of the African equator. Despite not having a completely "square tail", its naming highlights a distinguishing field mark. The similarly plumaged slender-tailed nightjar, found in dry bush country of the tropics, differs namely by its protruding central tail feathers. It is alternatively known as the Gabon nightjar or Mozambique nightjar.
This bird's call is a prolonged churring, which alternates between a fast and slow pace roughly every second. As such it differs from the similar long-tailed and slender-tailed nightjars which produce fast and slow churrs respectively.