Muhammad Ali
Muhammad AliReuters

Three-time world heavyweight boxing champion Muhammad Ali passed away Saturday morning, after he was hospitalized with severe breathing problems.

Seventy-four-year-old Ali's relatives were called to his bedside in order to say their goodbyes.

The legendary athlete suffered from Parkison's, which caused numerous respiratory complications.

US President Barack Obama said that he and his wife "pray that the greatest fighter of them all finally rests in peace."

Similarly, twice-champion George Foreman, who fought against Ali in the historic "Rumble in the Jungle" match, told the BBC, "The man was the greatest. Forget about boxing, he was one of the greatest men to appear on television, in the media."

Ali first won his world championship title in 1964 and defended it in 1967. When he refused to be drafted due to his religious beliefs, though, he lost the title and was sentenced to five years in jail.

Despite the setback, he again won the championship in 1974 and defended it yet again in 1978. In 1981, he retired due to the effects of Parkinson's.