John Atta Mills, who ran three times for president before being elected in the closest vote in Ghana's history on a platform vowing to reform the west African country, has died aged 68, officials said.
Chief of staff John Henry Martey Newman addressed the nation on state-run television stations, saying that Mr Atta Mills died on Tuesday afternoon at the 37th Military Hospital in Accra. He gave no details about the cause of death.
Information minister Fritz Baffour also declined to elaborate, but said: "Yes, I can confirm (his death), but I can't say more."
The president celebrated his 68th birthday on Saturday. He was poised to seek re-election later this year.
He travelled to the United States in March and met with US President Barack Obama at the White House. He also travelled to the US in April, as rumours about his health began to circulate in Ghana.
He was elected in a 2008 run-off vote and was to run for a second term in December. He campaigned on a platform of change, arguing that the western African country's growth had not been felt in people's wallets.
"People are complaining. They're saying that their standard of living has deteriorated these past eight years," he said. "So if Ghana is a model of growth, it's not translating into something people can feel."
The 2008 election was the third time that Mr Atta Mills had run for president.
He spent much of his career teaching at the University of Ghana. He earned a doctorate from London's School of Oriental and African Studies before becoming a Fulbright scholar at Stanford University in Palo Alto, California.