Events of 1455

• January 8 - Pope Nicholas V publishes Romanus Pontifex, an encyclical addressed to King Afonso V of Portugal, which sanctions the conquest of non-Christian lands, and the reduction of native non-Christian populations to 'perpetual slavery'.
• February 23 - The Gutenberg Bible is the first book printed with movable type.
• April 8 - Pope Calixtus III succeeds Pope Nicholas V as the 209th pope.
• The Wars of the Roses begin.
• May 18 - Battle of Arkinholm: King James II of Scotland defeats the Earl of Douglas.
• May 22 - First Battle of St Albans: Richard, Duke of York, defeats and captures King Henry VI of England.

Births

• February 2 - King John of Denmark, Norway, and Sweden (d. 1513)
• March 3 - King John II of Portugal (d. 1495)
• March 15 - Pietro Accolti, Italian Catholic cardinal (d. 1532)
• August 2 - John Cicero, Elector of Brandenburg (d. 1499)
• Peter Vischer the Elder, German sculptor (approximate date) (d. 1529)

Deaths

• February 18 - Fra Angelico, Italian painter (b. 1395)
• March 24 - Pope Nicholas V (b. 1397)
• April 1 - Zbigniew Cardinal Oleśnicki, Polish bishop and statesman (b. 1389)
• May 18 - Archibald Douglas, Earl of Moray (in battle)
• May 22 - Henry Percy, 2nd Earl of Northumberland, English politician (in battle)
• May 22 - Edmund Beaufort, 2nd Duke of Somerset, English commander (in battle) (b. 1406)
• May 22 - Humphrey Stafford, Earl of Stafford (in battle)
• September 3 - Alonso Tostado, Spanish Catholic bishop
• October 22 - Johannes Brassart, Flemish composer
• December 1 - Lorenzo Ghiberti, Italian sculptor and metal smith (b. 1378)
• December 2 - Isabel of Coimbra, queen of Portugal (b. 1432)