A casino (also known as a gambling establishment or a gaming hall) is a building in which people can gamble by playing games of chance or skill. Most casinos feature a variety of gambling games, including roulette, blackjack, craps, video poker, and slot machines. Some casinos also have restaurants, bars, and theaters. The precise origin of gambling is unknown, but it has been an activity in almost all human societies.

The earliest casinos were run by organized crime groups, who used proceeds from drug dealing, extortion, and other illegal rackets to finance the buildings and equipment. As the business expanded in the 1950s, legitimate businessmen were reluctant to invest in such a venture with its seamy image. But mobsters had plenty of cash from their illegal activities, and they took over Reno and Las Vegas. They made the casinos their own, taking sole or partial ownership of some and attempting to influence game outcomes through intimidation of personnel and threats of violence to casino patrons.

Modern casinos rely heavily on technology for security and supervision of games. For example, betting chips with microcircuitry allow casinos to monitor the exact amounts wagered minute-by-minute; roulette wheels are electronically monitored regularly to discover any statistical deviations from their expected results. In games where players compete against each other, such as poker, casinos earn money via a commission, or “rake,” taken from the pot. Some economists argue that the net impact of a casino on a local economy is negative, as it draws away spending on other forms of entertainment and hurts property values by drawing in problem gamblers.