Pope Callixtus III or Callistus III (31 December 1378 – 6 August 1458), born Alfons de Borja, was Pope from 8 April 1455 to his death in 1458. He is the first Pope from the House of Borgia, he was the uncle of the most scandalous Pope Alexander VI.

He became Pope at very advanced age, when he was 76 years old. He is viewed by historians as being extremely pious, and a firm believer in the authority of the Holy See.On 20 February 1456, Pope Callixtus III elevated two of his nephews to the position of cardinal. The first of them was Rodrigo de Borja ("Borgia" in Italian), who later became Pope Alexander VI (1492–1503), infamous for his alleged corruption and immorality.