In May 2012, Mr Chavez said he had recovered from an unspecified cancer, after undergoing surgery and chemotherapy in 2011 and a further operation in February 2012.
However, in December 2012, he announced he needed further cancer surgery in Cuba, and named his Vice-President, Nicolas Maduro, as his preferred successor should the need arise.
Since then he has struggled to recover and remained out of public view, finally returning to Venezuela in February.
In February 1992, Mr Chavez led a doomed attempt to overthrow the government of President Carlos Andres Perez amid growing anger at economic austerity measures.
The foundations for that failed coup had been laid a decade earlier, when Mr Chavez and a group of fellow military officers founded a secret movement named after the South American independence leader Simon Bolivar.
Relations with Washington reached a new low when he accused the Bush administration of "fighting terror with terror" during the war in Afghanistan after 11 September 2001.
Mr Chavez accused the US of being behind a short-lived coup that saw him removed from office for a couple of days in 2002.
He survived this episode and emerged strengthened two years later in a referendum on his leadership. He then went on to victory in the 2006 presidential election.
Mr Chavez's government has implemented a number of "missions" or social programmes, including education and health services for all. But poverty and unemployment are still widespread, despite the country's oil wealth.
Mr Chavez is renowned for his flamboyant public speaking style, which he has put to use in his weekly live TV programme, Alo Presidente (Hello President), in which he talks about his political ideas, interviews guests and sings and dances.