Muhammad Ali vs. Leon Spinks, was a professional boxing match contested on February 15, 1978 in Las Vegas for the Undisputed Heavyweight Championship. After his unanimous decision victory against Earnie Shavers, Muhammad Ali decided to face 1976 Olympic Gold medalist Leon Spinks, knowing that he'd have to face Ken Norton for the fourth time or lose his WBC belt, after the No 1 ranked Norton beat No 2 ranked Jimmy Young in a title eliminator in November 1977. The 10–1 underdog Spinks ended up winning two of the scorecards 145–140 and 144–141, while the third was 142–143 giving him a split decision win and making him the Undisputed Heavyweight Champion after only eight professional bouts, and the only man ever to take a title from Ali inside the ring. Sports Illustrated covered the bout, and with that historic upset put Leon Spinks on the cover.

A rematch took place on September 15, 1978, for the WBA and Lineal Heavyweight Champion titles, with Ali regaining the title with a Unanimous Decision.