1242Centuries: 12th century - 13th century - 14th century
- April 5 - During a battle on the ice of Chudskoye Lake, Russian forces rebuff an invasion attempt by the Teutonic Knights.
- Emperor Go-Saga ascends to the throne of Japan.
- Batu Khan establishes the Golden Horde at Sarai.
- Cleves, Germany is chartered as a city.
- Kiel, Germany is chartered as a town.
- The diocese of Warmia, Poland is created.
- The archbishop of Wiesbaden conquers the city from the Duke of Nassau.
- The Mongols invade the Seljuk sultanate.
- German colonists arrive in Bratislava after the Mongols fail to conquer the city.
- Timeline of medicine and medical technology - Ibn Nafis suggests that the right and left ventricles of the heart are separate and describes the lesser circulation of blood.