Fifty-two people are killed during an arson attack caused by members of the drug cartel Los Zetas.

On August 25, 2011, members of the drug cartel Los Zetas set a casino on fire in Monterrey, Nuevo León, Mexico, killing 52 people.

Los Zetas is a Mexican criminal syndicate and designated terrorist organization, known as one of the most dangerous of Mexico's drug cartels. They are known for engaging in brutally violent "shock and awe" tactics such as beheadings, torture, and indiscriminate murder. While primarily concerned with drug trafficking, the organization also ran profitable sex and gun rackets. Los Zetas also operated through protection rackets, assassinations, extortion, kidnappings and other illegal activities. The organization was based in Nuevo Laredo, Tamaulipas, directly across the border from Laredo, Texas. The origins of Los Zetas date back to the late 1990s, when commandos of the Mexican Army deserted their ranks and began working as the enforcement arm of the Gulf Cartel. In February 2010, Los Zetas broke away and formed their own criminal organization, rivalling the Gulf Cartel.

August 25 is the 237th day of the year in the Gregorian calendar; 128 days remain until the end of the year.