LeBron James made the announcement during a live primetime television special on ESPN this evening.

"I don't have any doubts at all," he told ESPN's Jim Gray. "I've slept enough, or the lack of sleep."

James' announcement was met by euphoria from fans in Miami and anger in Cleveland, where the superstar spent his first seven NBA seasons after high school stardom in nearby Akron, Ohio.

James said he informed the Heat of his decision only moments before his appearance on the 9 p.m. ET ESPN special, that he had not given advance word to the other teams bidding for his services, and that the number of people who knew of his decision in advance could be counted on the fingers of one hand.

"I feel like this is going to give me the best opportunity to win and to win for multiple years," James said, explaining why he will join fellow free agents Dwyane Wade and Chris Bosh in Miami. "I want to be able to win championships."