Leonardo da Vinci's ornithopter was an aircraft concept designed to imitate a bird's flapping wings.
Leonardo studied birds and bats because he believed their movement could reveal principles for human flight. His ornithopter sketches show a pilot positioned inside or beneath a framework, using mechanical components to move broad wings. Several versions appear in his notebooks rather than one single finalized machine.
The word ornithopter means a craft that flies by flapping wings. Leonardo's proposals were not powered by an engine; some depended on a pilot's arms or legs. Human muscle power was not sufficient to lift a practical man-carrying machine of the size he imagined.
Leonardo's work nevertheless contributed careful observations about wing structure, balance, and air movement. Modern ornithopters have been built as small experimental aircraft and models, but they do not make Leonardo's full-scale Renaissance designs successful flying machines.