Castro was born August 13, 1926, in Oriente Province in eastern Cuba. His father, Angel, was a wealthy landowner originally from Spain; his mother, Lina, had been a maid to Angel's first wife.
Though he grew up in wealthy circumstances, Oriente was a poor area wracked by a peasant rebellion in Fidel Castro's formative years, which is thought to have influenced his political leanings.
Educated in Jesuit schools, Castro earned a law degree from the University of Havana and offered free legal services to the poor. In 1952, at the age of 25, he ran for the Cuban parliament.
But just before the election, the government was overthrown by Fulgencio Batista, who established a dictatorship that put Castro on the road to revolution.
In 1953, Castro was one of about 150 fighters who attacked a military barracks in an unsuccessful attempt to overthrow Batista. The attack made him famous throughout Cuba, but it also earned him a prison sentence.
He was released in 1955 and lived in exile in the United States and Mexico, where he organized a guerrilla group with Raúl Castro and Ernesto "Che" Guevara, an Argentine doctor-turned-revolutionary.
The next year, 81 fighters landed in Cuba. Most were killed; the Castros, Guevara and other survivors fled into the Sierra Maestra Mountains along the southeastern coast, where they waged a guerrilla campaign against the Batista government that finally brought it down in 1959.
Although the United States quickly recognized the new Cuban government, tensions arose after Castro began nationalizing factories and plantations owned by American companies. In January 1961, Washington broke off diplomatic ties.
Less than four months later, a group of CIA-trained Cuban exiles, armed with U.S. weapons, landed at the Bay of Pigs in Cuba in a disastrous attempt to overthrow Castro.
Two weeks after the Bay of Pigs, Castro formally declared Cuba a socialist state.
In October 1962, Cuba became the focus of a tense world crisis after the Soviet Union installed nuclear weapons in the country. President Kennedy demanded that the Soviets remove them and quarantined the island, bringing the world to the brink of nuclear war.
The Soviet Union backed down and removed the weapons.
Through the years, Castro was the target of scores of CIA assassination attempts. He took delight in the fact none of them ever succeeded.
"I have never been afraid of death. I have never been concerned about death," he once said.
As for Castro's private life, he is believed to have fathered eight children with four women. His longtime companion, Dalia Soto del Valle, is the mother of five of his sons.