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)

• Nicholas Barnham, Knight, killed in the War of the Roses (d. 1485)

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)