A casino is a gambling establishment with a wide range of tables and machines where patrons may place wagers on games of chance. It is also called a gaming house or simply a gambling hall. Casinos are popular with tourists and business travelers. In the United States casinos are mainly located in Las Vegas and Atlantic City, but also exist in New Jersey and many Indian reservations.

While the precise origin of gambling is unknown, evidence suggests it has been practiced in almost all societies throughout history. Modern casino gambling began in the United States during the 19th century, when riverboats brought gambling to Atlantic City and other cities along the East Coast. Casinos gradually spread throughout the country as state legislatures changed laws to permit them. By the end of the 20th century, nearly 40 states had legalized casinos.

Some of the most famous casinos in the world are in Europe, such as Monte Carlo, the glitzy casino built for the princely family of Monaco. It was featured in several James Bond movies and is still a major source of income for the principality. Other popular European casinos include those in Estoril, Portugal; Corfu, Greece; and Baden-Baden and Bad Homburg von der Hohe, Germany.

Because of the large amounts of money handled within a casino, both patrons and staff may be tempted to cheat or steal, either in collusion with each other or independently. To prevent this, most casinos employ security measures, such as cameras and guards. Some casinos also provide special inducements to big bettors, such as free spectacular entertainment and elegant living quarters.