The 1540s was a decade that started on 1 January 1540 and ended on 31 December 1549.

It is distinct from the decade known as the 155th decade which began on January 1, 1541 and ended on December 31, 1550.

• Hernando de Soto is the first European to see the Mississippi River.
• Ivan IV of Muscovy becomes the first Tsar of Russia.
• Edward VI succeeds his father Henry VIII as King of England.
• Wars between Protestants and Catholics in Europe.
• Japan opens up to Europeans.

• El Greco, Greek-born artist
• Mary, Queen of Scots
• Miguel de Cervantes, Spanish writer

• Martin Luther, reformer
• Hernando de Soto, Spanish explorer
• Henry VIII, King of England
• Hernán Cortés, Spanish explorer
• Juan Diego Cuauhtlatoatzin, Mexican Catholic saint