Osiel Cárdenas Guillén (born 18 May 1967) is a Mexican drug lord and the former leader of the Gulf Cartel and Los Zetas.
Originally a mechanic in Matamoros, Tamaulipas, he entered the cartel by killing Juan García Abrego's friend and competitor Salvador Gómez, after the former's arrest in 1996.
As confrontations with rival groups heated up, Osiel Cárdenas sought and recruited over 30 deserters from the Grupo Aeromóvil de Fuerzas Especiales to form the cartel's armed wing.
Los Zetas served as the hired private mercenary army of the Gulf Cartel.
After a shootout with the Mexican military in 2003, Cárdenas was arrested and imprisoned.
In 2007 he was extradited to the U.S.
and in 2010 he was sentenced to 25 years in prison for money laundering, drug trafficking, homicide, and for having threatened two U.S.
federal agents in 1999.
His brother, Mario Cárdenas Guillén, worked for the Gulf Cartel, as did another brother, Antonio Ezequiel Cárdenas Guillén, who was killed by Mexican Marines on 5 November 2010.
He is currently imprisoned at USP Florence High with a release date of 2025.