Swimming flippers, swimming flippers, flippers or flippers are flipper shaped accessories worn by feet and legs, made of rubber, plastic or a combination of these materials, which can help to move in water during water sports, such as swimming, surfboard, surfing, kneepad, river skateboard, underwater hockey, underwater rugby and various other types of underwater diving.

Swimming fins help the wearer to travel more effectively through the water because the feet are too small and shaped to provide a lot of thrust, especially when the wearer is carrying equipment that increases hydrodynamic resistance. Free divers use long fins and single fins as underwater propulsion means, without high-frequency leg movement. This improves efficiency and helps reduce oxygen consumption. Short, rigid fins are very effective for short-term acceleration and maneuvering, and are useful for body surfing.