Sergio Gabriel Martínez (born February 21, 1975 in Quilmes, Buenos Aires, Argentina) is an Argentine professional boxer . He is the former Ring and WBC Middleweight Champion. Martinez was previously in the light middleweight division, where he held the WBC Light Middleweight title (Interim then elevated to full status champion), as well as the WBC Latino title. Also, he has competed in the welterweight division, where he held the WBO Latino title. In 2010, Martínez received The Ring and BWAA "Fighter of the Year" and The Ring "Knockout of the Year" awards, resp. Martinez recently announced his retirement from the sport of boxing. He is also part owner of a fitness company named Brooklyn FitBoxing.