Marvelous Marvin Hagler is a former professional boxer and film actor. Hagler competed in boxing from 1973 to 1987. He reigned as undisputed middleweight champion from 1980 to 1987, making twelve successful defenses of that title, and holds the highest knockout percentage of all undisputed middleweight champions, at 78%, while also holding the Third-longest unified championship reign in boxing history at twelve consecutive defenses.

The previous records still hold as of February 2021. At six years and seven months, his reign as undisputed middleweight champion is the second-longest of the last century, behind only Tony Zale, whose reign included several years of inactivity during his service in World War II. Many analysts and boxing writers consider Hagler to have one of the most durable chins in boxing history, having been knocked down only once during the entire professional career, and the scored knockdown is still being disputed. He was named Fighter of the Decade (1980s) by Boxing Illustrated magazine, and twice named Fighter of the Year by The Ring magazine and the Boxing Writers Association of America.

Hagler is an inductee of the International Boxing Hall of Fame and the World Boxing Hall of Fame. In 2001 and 2004, The Ring named him the fourth greatest middleweight of all time and in 2002 named him the 17th greatest fighter of the past 80 years. After boxing, Hagler moved to Italy to star in movies.