Singer James Brown, known as the "Godfather of Soul", has died at the age of 73, his agent has said.
Brown was "a gifted genius when it came to music", his agent said
He was admitted to hospital in Atlanta after being diagnosed with severe pneumonia but died at 0145 local time (0645 GMT), said Frank Copsidas.
The star was famous for hits including I Got You (I Feel Good), Papa's Got a Brand New Bag and Living in America.
"He is such an influence, I learned so much from him," Mr Copsidas told the BBC World Service.
"On Friday he had his toy giveaway, which is his annual toy giveaway in Augusta, Georgia.
"On Saturday, he went to his dentist up in Atlanta, and his dentist told him something was wrong, and he sent him to a doctor immediately."
String of hits
Brown was born in 1933 in South Carolina.
He joined a gospel group as a young man after his release from jail for trying to steal a car.
He had his first hit on the US rhythm and blues chart, Please Please Please, in 1956.
Brown had 94 hits on Billboard's mainstream Hot 100 in the US, according to his official website, and by the end of his career, he had a repertoire of 800 songs.
However, he achieved only one top 10 single in the UK - Living in America, from the soundtrack of Rocky IV, which reached number five in 1986.
The star was credited with spreading the popularity of funk around the world, influencing a new generation of black music which spawned rap and hip-hop.
Brown, who had surgery for prostate cancer in 2004, appeared in London in October as part of the BBC's Electric Proms line-up.
Hall of Fame
At the time, he described how he planned to carry on as a performer, saying: "Everyone's got soul, whether it's talking, hip-hop, rap, gospel.
"I don't wanna change, because then I'd have to name myself Sam Smith or Ted Wright or somebody. I'm going to be James Brown."
Last month Brown played at a ceremony at London's Alexandra Palace which saw his induction into the UK Music Hall of Fame, 20 years after entering the US equivalent.
Brown won the Award of Merit at the American Music Awards in 1992
"He was dramatic to the end, dying on Christmas Day," said US civil rights leader Jesse Jackson, who has been a friend of Brown since 1955.
"He'll be all over the news all over the world today. He would have it no other way," he told Associated Press.
Former BBC Radio 1 DJ Andy Peebles said he was "a one-of-a-kind, never-to-be-repeated star".
Connor McNicholas, editor of the NME music magazine, said Brown appealed to successive generations.
"This was a guy who came from a very deprived background, and knew that the route to success was young music buyers, so as every generation went through he was very keen to make sure that he updated his sound and made sure that he stayed relevant."
And Bob Harris of BBC Radio 2 described Brown as a "massive influence, not just for black music but also for so many white music fans who were so strongly motivated and influenced by the music he made".