Leonardo da Vinci designed ornithopters, aircraft intended to fly by flapping wings.
The word ornithopter means a flying machine whose wings imitate the flapping action of birds or insects. Leonardo studied bird anatomy, wing structure, balance, and airflow in notebooks while trying to understand human flight. Some of his designs placed a pilot in a frame connected to large movable wings.
Leonardo recognized that a person could not simply flap large wings with arm strength alone. His designs explored foot pedals, levers, and mechanical linkages to multiply the pilot's effort. There is no evidence that one of his ornithopters achieved successful human flight.
An ornithopter is distinct from Leonardo's parachute and his screw-shaped aerial machine. Those concepts rely on different principles: descent under a canopy and rotary lift, rather than flapping wings.