Which Leonardo da Vinci design used flapping wings inspired by birds?

Leonardo da Vinci’s bird-inspired flying-machine design using flapping wings was an ornithopter.

An ornithopter is an aircraft intended to fly by repeatedly moving its wings, imitating the motion of birds or bats. Leonardo filled his notebooks with observations of birds, wing structures, air currents, and the mechanics of flight. Those studies informed several proposed machines.

Leonardo’s ornithopter designs generally placed a human pilot inside or beneath a framework connected to large wings. The pilot would provide movement through pedals, levers, or other mechanical actions. Human muscle, however, cannot supply enough power for a practical machine of that scale.

The term is broader than Leonardo’s work: many inventors later explored flapping-wing aircraft. Leonardo’s designs are historically important because they combined close anatomical observation with mechanical engineering, even though none became a successful piloted aircraft.