A casino (also spelled ca*si*nos or casin) is an establishment which offers a variety of gambling opportunities, such as slot machines and table games. Some casinos also offer luxury hotel rooms, restaurants, and entertainment shows. The largest casinos are designed to impress, with opulent architecture, enormous indoor space, and sprawling grounds. Some of these casinos feature five-star hotel accommodations, Michelin-starred restaurants, and designer shops. Others host top-billed entertainment events, from circus acts and comedians to the latest musicians topping the Billboard charts.

In some countries, such as the United States, casinos are legally permitted on American Indian reservations, where state antigambling laws do not apply. From the 1980s, casinos have also been built on riverboats and in other locations not subject to state regulations.

Most casino games are conducted by live dealers and involve a combination of strategy and chance. They are generally played against the house, which gains a profit as a percentage of total wagers, or the bankroll of those playing the game. Casinos employ mathematicians and computer programmers who study the house edge and variance of their games in order to maximize profits. These people are known as gaming mathematicians and gaming analysts.

The Bellagio in Las Vegas is widely considered to be the most famous casino in the world, although there are several others that attract discerning players. Among these are the Casino de Montreal, which features high-end hotels and luxury spas; the Casino Lisboa in Lisbon, which is sleek and modern; and the City of Dreams in Macau, a massive complex featuring a huge array of slots and table games.