Leonardo da Vinci designed the aerial screw, a helical flying machine often regarded as a precursor to the helicopter.
Drawn around 1489, the aerial screw has a large spiral surface made from reeds, linen, and wire. Leonardo reasoned that if the spiral rotated quickly enough, it might screw itself upward through the air, much as a screw moves through a solid material.
The idea was ingenious but not practical with the materials and power sources available in Renaissance Italy. The design had no engine, and the proposed human-powered mechanism could not generate enough lift to raise the heavy frame. Modern models can demonstrate the principle, but they do not prove that Leonardo’s original machine could have flown.
The aerial screw is sometimes called the first helicopter. That description is useful as a comparison, not as a claim that Leonardo built a working helicopter. It was a conceptual study of vertical flight, created centuries before powered rotorcraft became feasible.