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Year 1334 (MCCCXXXIV) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar.

• July 18 – The bishop of Florence blesses the first foundational stone laid for the new campanile (bell tower) of the Florence Cathedral (the tower was designed by the artist Giotto di Bondone).
• December 30 – Pope Benedict XII succeeds Pope John XXII, as the 197th pope.

• Autumn – Battle of Adramyttion: A Christian league defeats the fleet of the Turkish Beylik of Karasi.

• January 4 – Amadeus VI of Savoy (d. 1383)
• January 13 – King Henry II of Castile (d. 1379)
• May 25 – Emperor Sukō (d. 1398)
• August 30 – King Pedro of Castile (d. 1369)
• date unknown
  • King James I of Cyprus (d. 1398)
  • Margaret Graham, Countess of Menteith, Scottish noble (d. c. 1380)
  • Hayam Wuruk, Javanese ruler (d. 1389)

• January 17 – John of Brittany, Earl of Richmond (b. c. 1266)
• December 4 – Pope John XXII (b. 1249)^[1]
• date unknown – Sheikh Safi-ad-din Ardabili of Persia (b. 1251)
• Isabella de Vesci, politically active French noblewoman (b. 1260s)