Leonardo da Vinci’s armored military vehicle design is commonly called a tank.
Leonardo sketched the vehicle around 1487–1489 while working for Ludovico Sforza, Duke of Milan. Its conical, turtle-like shell was intended to protect soldiers inside while the vehicle moved across a battlefield. Several small cannons were arranged around the vehicle so it could fire in multiple directions.
The design was powered by people turning cranks connected to wheels. In its surviving form, the gearing would make the wheels turn in the wrong direction, so historians often interpret that detail as a drawing error, a deliberate security flaw, or an unfinished concept. The vehicle was never built as a functioning fifteenth-century tank.
The modern word “tank” was not used for Leonardo’s design. British forces adopted that term as a wartime code name during World War I, centuries later. Leonardo’s vehicle is therefore best understood as an early armored fighting-vehicle concept, not a direct working predecessor of modern tanks.