The year 1502 in science and technology included many events, some of which are listed below.
- January 1 – Portuguese explorers, led by Pedro Álvares Cabral, sail into Guanabara Bay, Brazil, mistaking it for the mouth of a river, which they name Rio de Janeiro.
- May 11 – Christopher Columbus leaves Cadiz, Spain for his fourth and final voyage to the New World.
- May 21 – Portuguese navigator João da Nova discovers the uninhabited island of Saint Helena.
- August 14 – Columbus lands at Trujillo and names the country 'Honduras'.
- September 18 – Columbus lands in Costa Rica.
- Amerigo Vespucci, on his return to Lisbon from a voyage to the New World, writes a letter, Mundus Novus, to Lorenzo de' Medici indicating that South America must be an independent continent.
- The Cantino planisphere is the first known world map showing Portuguese discoveries.