Muhammad Ali died from septic shock and went peacefully, a spokesman for the family said.
He'd been in hospital in Arizona for a few days, with his family gathered around. They had a full day to say their final goodbyes to the 74 year-old.
Ali's family have this morning announced that his funeral will span two days, beginning with a private family service on Thursday, US time.
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Family spokesman Bob Gunnell says an Imam will lead the public service the following day in his hometown in Kentucky.