Ali was released Tuesday night from an undisclosed hospital and "is in great spirits," family spokesman Bob Gunnell told the Associated Press.
Ali was hospitalized on Dec. 20 with what was initially diagnosed as pneumonia. Doctors later determined he had a urinary tract infection, Gunnell said.
Gunnell said Ali is back "to his normal routine" and that the three-time heavyweight champion is looking forward to celebrating his upcoming 73rd birthday on Jan. 17 with family and friends.
Ali and his wife, Lonnie, have homes in Paradise Valley, Ariz.; Berrien Springs, Mich; and in Louisville, Ky. Gunnell would not say which of his homes Ali had returned to.
Ali has not made many public appearances in recent years as he continues his battle with Parkinson's disease, but he did attend a ceremony for the Muhammad Ali Humanitarian Awards alongside Football Hall of Famer Jim Brown in Louisville in September.
Ali is considered one of the greatest boxers of all time. He retired from professional boxing in 1981 with a 56-5 career record. Since his retirement, he has been an advocate for social and humanitarian causes.