A casino is an establishment that offers gambling activities. Some casinos are built with the purpose of entertaining their guests and have restaurants, luxury accommodations, retail shops and other facilities. Most casinos also have a special department for security, which is able to prevent and deter crime on the premises. Modern casino security is usually divided into a physical force and a specialized surveillance department, both of which work closely together to make the casino as safe as possible for patrons.

Gambling in one form or another has been part of almost every culture across the world and throughout history. The ancient Mesopotamian and Greek civilizations, the Roman Empire and Elizabethan England all had casino-like entertainment venues. Modern casinos are large and often combined with hotels, resorts, restaurants, nightclubs and other tourist attractions.

The defining characteristic of a casino is that it offers a virtual assurance of gross profit, as long as the games are played within an established limit. This virtual guarantee is what attracts many of the biggest gamblers to casinos, who are sometimes offered extravagant inducements such as free spectacular entertainment and luxurious living quarters. Lesser bettors are offered reduced-fare transportation, free hotel rooms and a variety of other incentives.

The most famous casinos in the world are in Las Vegas and Atlantic City, but there are now over 40 legal gambling zones in the United States and many more around the world. In Macau, for example, which is the only part of China where gambling is legal, casinos have become a major draw and helped transform this former Portuguese colony into an international entertainment capital.