Fidel Alejandro Castro Ruz (born August 13, 1927) is the former Head of State of Cuba, a position which he held for nearly 50 years, and a leader of the Cuban Revolution. Fidel Castro, as he is widely known, was the Prime Minister of Cuba from February 1959 to December 1976 and then President of the Council of State of Cuba until he transferred power to his brother Raúl Castro in February 2008.

He was born to a millionaire Spanish father and went to the most elite schools. He started a political career at early age and was a recognized figure in politics. He ran democratically for parliament in 1952 elections. Opposing Fulgencio Batista, he eventually led the failed 1953 attack on the Moncada Barracks, after which he was captured, tried, incarcerated and later released. He then traveled to Mexico to organize and train for an assault on Batista's Cuba. He and his fellow revolutionaries left Mexico for the East of Cuba in December 1956.

Castro came to power as a result of the Cuban revolution that overthrew the U.S-backed dictator Fulgencio Batista,, and shortly became Prime Minister of Cuba, replacing professor José Miró Cardona.

Instead of filling his initial promise, to have democratic elections "within months", he delayed them and eventually abolished them. Castro purged labor unions, moderates, took control of the media, and loyalty to him became the primary criteria for all appointments. In 1965 he became First Secretary of the Communist Party of Cuba and led the transformation of Cuba into a one-party socialist republic. In 1976 he became President of the Council of State as well as of the Council of Ministers. He also held the supreme military rank of Comandante en Jefe ("Commander in Chief") of the Cuban armed forces. Castro's failure to restore democracy led to conflicts with many of his former supporters - even his own sister denounced the "enormous prison surrounded by water".

Following intestinal surgery from an undisclosed digestive illness believed to have been diverticulitis, Castro transferred his responsibilities to the First Vice-President, his younger brother Raúl Castro, on July 31, 2006. On February 19, 2008, he announced he would "neither aspire to nor accept the positions of President of the State Council and Commander in Chief". On February 24, 2008, the presidency was transferred to his brother Raúl Castro. Fidel Castro remains First Secretary of the Communist Party.

Many describe him as a dictator and his rule has been the longest ever in modern Latin American history. Human rights organizations accuse him of creating a "repressive machinery".