A casino (Spanish: casino) is an establishment for gambling. It may also refer to a place where people play games of chance for money or other rewards, such as free food, drinks, or lodging. Some casinos are large and resemble hotels, while others are small and resemble bars or restaurants. Casinos are usually regulated by government bodies, either at the local or state level.

A large percentage of the population is involved in casino gambling at least occasionally. Some gamble on their own, while most go to the casino with family and friends or as part of organized groups such as church groups or social clubs. In a 2002 survey of Nevada citizens by Gemini Research, respondents who admitted to casino gambling at least once a month were asked which games they most liked to play. The majority (50%) chose slot machines, followed by card games (31%), and then table games (15%). Other casino games such as keno, bingo, and gambling on sports or racing events received much lower levels of player preference.

The economic mainstay of many American casinos is the income derived from the use of automated machine games, especially slot machines and video poker. These games can be played for very low sums, at a rate of one or more spins per minute, and generate large amounts of cash in a short period of time. The casino profits by allowing players to make bets on the outcome of a single spin or a series of spins, and by charging commissions on these wagers. To maximize profits these games must be properly calibrated and monitored regularly for statistical deviations from their expected results. Mathematicians and computer programmers who work on this type of analysis for casinos are known as gaming mathematicians or gambling analysts.