Most title-fight rounds contested in a boxing career

The most title-fight rounds contested in a boxing career is 339 by Emile Griffith (USA, b.3 February 1938; d.23 July 2013) in 26 title fights between 1 April 1961 and 18 September 1976.

Emile Griffith was a welterweight boxer and fought 10 world champions during his career. His most infamous title fight was his third bout against Benny Paret in 1962. Griffith gave Paret "an unmerciful beating" in the final round, putting his opponent in a coma (he died 10 days later). He entered the International Boxing Hall of Fame in 1990 and was described as a gentleman outside of the ring. Following retirement from boxing, he worked as a corrections officer in a Juvenile Detention Facility.