The Gulf Cartel (Cártel del Golfo) is a Mexican drug trafficking organization (MDTO) based in Matamoros, Tamaulipas. Heavy operations also include the cities of Reynosa and Nuevo Laredo. Its chief rival is the Sinaloa Cartel. The Gulf Cartel traffics cocaine, marijuana, methamphetamine and heroin across the border to major cities in the United States. The group is known for its violent methods and intimidation, and works closely with corrupt law officials and business people in Mexico as well as in the United States. The sphere of influence for the cartel has been determined to be from the Gulf Coast state of Tamaulipas to Piedras Negras, Coahuila.

Aside from earning money from the sales of narcotics, the Cartel also collects taxes aka piso, cuota from street level dealers, prominent businesses. Anyone passing narcotics or aliens through a plaza belonging to the Gulf Cartel is subject to payment of these ‘taxes’ to the cartel, regardless of whether the contraband is subsequently apprehended by US law enforcement or not. Payment of these taxes assure that the Cartel will not strike violently at those who pay them. The Gulf cartel does not limit itself solely to narcotics trafficking, as they have been known to kidnap local businessmen to collect money.