Pope John XXIII excommunicates Fidel Castro.

Pope John XXIII was head of the Catholic Church and sovereign of the Vatican City State from 28 October 1958 until his death on 3 June 1963. He is the most recent pope to take the pontifical name "John".

Fidel Alejandro Castro Ruz was a Cuban politician and revolutionary who was the leader of Cuba from 1959 to 2008, serving as the prime minister of Cuba from 1959 to 1976 and president from 1976 to 2008. Ideologically a Marxist–Leninist and Cuban nationalist, he also served as the first secretary of the Communist Party of Cuba from 1965 until 2011. Under his administration, Cuba became a one-party communist state; industry and business were nationalized, and socialist reforms were implemented throughout society.

January 3 is the third day of the year in the Gregorian calendar; 362 days remain until the end of the year.