The Gulf Cartel (Spanish: Cártel del Golfo [ˈkaɾtel ðel ˈɣolfo], or Golfos) is a criminal syndicate, drug trafficking organization, and U.S.-designated terrorist organization, which is perhaps one of the oldest organized crime groups in Mexico. It is currently based in Matamoros, Tamaulipas, directly across the U.S. border from Brownsville, Texas.

Their network is international, and is believed to have dealings with crime groups in Europe, West Africa, Asia, Central America, South America, and the United States. Besides drug trafficking, the Gulf Cartel operates through protection rackets, assassinations, extortions, kidnappings, and other criminal activities. The members of the Gulf Cartel are known for intimidating the population and for being particularly violent.

Although its founder Juan Nepomuceno Guerra smuggled alcohol in large quantities to the United States during the Prohibition era, and heroin for over 40 years, it was not until the 1980s that the cartel was shifted to trafficking cocaine, methamphetamine and marijuana under the command of Juan Nepomuceno Guerra and Juan García Ábrego.

The Gulf Cartel, a drug cartel based in Matamoros, Tamaulipas, Mexico, was founded in the 1930s by Juan Nepomuceno Guerra. Originally known as the Matamoros Cartel (Spanish: Cártel de Matamoros), the Gulf Cartel initially smuggled alcohol and other illegal goods into the U.S. Once the Prohibition era ended, the criminal group controlled gambling houses, prostitution rings, a car theft network, and other illegal smuggling. It grew significantly in the 1970s under the leadership of kingpin Juan García Ábrego.

By the 1980s, García Ábrego began incorporating cocaine into the drug trafficking operations and started to have the upper hand on what was now considered the Gulf Cartel, the greatest criminal dynasty in the US-Mexico border. By negotiating with the Cali Cartel, García Ábrego was able to secure 50% of the shipment out of Colombia as payment for delivery, instead of the US$1,500 per kilogram they were previously receiving. This renegotiation, however, forced Garcia Ábrego to guarantee the product's arrival from Colombia to its destination. Instead, he created warehouses along the Mexican's northern border to preserve hundreds of tons of cocaine; this allowed him to create a new distribution network and increase his political influence. In addition to trafficking drugs, García Ábrego would ship cash to be laundered, in the millions. Around 1994, it was estimated that the Gulf Cartel handled as much as "one-third of all cocaine shipments" into the United States from the Cali Cartel suppliers. During the 1990s, the PGR (Procuraduría General de la República), the Mexican attorney general's office, estimated that the Gulf Cartel was "worth over US$10 billion."

García Ábrego's ties extended beyond the Mexican government corruption and into the United States. With the arrest of one of García Ábrego's traffickers, Juan Antonio Ortiz, it became known the cartel would ship tons of cocaine in the United States Immigration and Naturalization Service (INS) buses between the years of 1986 to 1990. The buses made great transportation, as Antonio Ortiz noted since they were never stopped at the border.

It also became known that, in addition to the INS bus scam, García Ábrego had a "special deal" with members of the Texas National Guard who would truck tons of cocaine and marijuana from South Texas to Houston for the cartel.

Garcia Abrego's reach became known when a United States Federal Bureau of Investigation (FBI) agent named Claude de la O, in 1986, stated in testimony against García Ábrego that he received over US$100,000 in bribes and had leaked information that could have endangered an FBI informant as well as Mexican journalists. In 1989 Claude was removed from the case for unknown reasons, retiring a year later. García Ábrego bribed the agent in an attempt to gather more information on U.S. law enforcement operations.