Leonardo da Vinci studied an ornithopter, an early aircraft concept using flapping wings inspired by birds and bats.
In the late 15th century, he filled notebooks with observations of bird flight, wing shapes, balance, and the movement of air. His proposed flying machines generally relied on a person inside the frame to operate wings through pedals, levers, or other mechanisms. The designs show careful interest in anatomy and aerodynamics, even though the available materials and human muscle power were insufficient for sustained powered flight.
An ornithopter is defined by flapping wings, not by the presence of an engine or a particular body shape. Leonardo also investigated gliding and parachute-like ideas, so not every flying-machine drawing belongs to the ornithopter category. No Leonardo ornithopter is known to have flown successfully, and his work remained a study of flight rather than a working aircraft.