Leonardo da Vinci designed a compass using a magnetized needle to show direction.
A magnetic compass works because a freely rotating magnetized needle aligns approximately with Earth’s magnetic field. Leonardo’s notebooks contain studies of magnetic needles and directional instruments, reflecting his interest in navigation, surveying, and the physical behavior of magnets.
Leonardo did not invent the compass. Magnetic direction-finding instruments were known in China centuries earlier and had reached Europe before his lifetime. His importance lies in examining and improving instruments within the scientific and engineering culture of Renaissance Italy.
A compass is not the same as an astrolabe. An astrolabe helps measure the positions of celestial bodies, while a magnetic compass indicates direction relative to magnetic north.