A family spokesman for Muhammad Ali says the boxing great has been released from a hospital after recovering from a severe urinary tract infection.

Ali spokesman Bob Gunnell said the three-time world heavyweight champion is back home after being released from an undisclosed hospital on Tuesday night. Ali has been waging a battle with Parkinson's disease for years.

Ali was hospitalised in December with what was initially believed to be a mild case of pneumonia. But Mr Gunnell says doctors later determined that the 72-year-old Ali was suffering from a severe urinary tract infection and not pneumonia.

Mr Gunnell says Ali has fully recovered and is looking forward to celebrating his birthday on January 17 with family and friends.

He says the Ali family appreciates the outpouring of support and well wishes.