Fast and Furious is a gunwalking sting operation conducted by the Bureau of Alcohol, Tobacco and Firearms (ATF) to track the flow of guns from the United States into the hands of Mexican drug cartels. Gunwalking or "letting guns walk" was a tactic used by ATF to knowingly allow thousands of guns to be bought by suspected arms traffickers (gunrunners) working through straw purchasers on behalf of Mexican drug cartels. The stated goal of gunwalking was to track the firearms as they were transferred to higher-level traffickers and key operatives in Mexican cartels, in theory leading to their arrests and the dismantling of the cartels.

However many firearms sold through the Fast and Furious operation went missing and some turned up at violent crime scenes on both sides of the Mexico–United States border, including the scene of the killing of Customs and Border Patrol Agent Brian Terry.

The operation became quite controversial in both Mexico and the U.S. which led to calls in congress for the resignation of Attorney General Eric Holder, U.S. top law enforcement official. President Barack Obama also invoked executive privilege in order to prevent turning over documents to Republicans in Congress involved with the botched gun-smuggling investigation.