What was Leonardo da Vinci’s proposed flapping-wing aircraft called?

Leonardo da Vinci’s proposed flapping-wing aircraft was an ornithopter.

An ornithopter is an aircraft designed to fly by flapping wings, in imitation of birds or bats. Leonardo studied bird flight extensively and filled notebooks with observations about wing movement, balance, air currents, and the relationship between weight and lift. Several of his flying-machine sketches use mechanical arrangements intended to move wings through a flapping cycle.

Leonardo’s ornithopter designs were not powered by an engine. Some depended on a person’s muscles, while others imagined mechanical transmission systems. Human muscle power is not sufficient to lift a person using a bird-sized flapping mechanism, so these designs could not function as practical aircraft in their proposed form.

The term is broader than Leonardo’s work: modern experimental ornithopters have flown, including small radio-controlled models. Leonardo’s contribution was his unusually detailed attempt to connect biological flight with mechanical engineering.