A casino is an establishment where people can play gambling games. It is sometimes called a gambling house, and in some countries it is illegal to operate such an establishment without a license. In modern usage, the word is almost always used in the sense of a large building which houses gambling activities, but there have been less lavish places that have been called casinos (and still are).

While the precise origin of casino gambling is unknown, it is believed to be as old as human civilization itself. In fact, there are traces of gambling activity in almost every culture throughout history.

Most modern casinos feature a wide range of gambling opportunities, including slot machines and table games. In addition, they offer a variety of dining options and other entertainment. Most modern casinos also employ several security measures to deter criminals and cheaters. These measures include video surveillance and the use of special security chips with built-in microcircuits. Some casinos also have catwalks in the ceiling that allow security personnel to look down on tables and slot machines through one-way glass.

Successful casinos generate billions of dollars in annual revenues for the companies, investors, and Native American tribes that own them. They also provide substantial revenue streams for state and local governments, which often subsidize their operations. Because of the large amounts of money that are handled in casinos, both patrons and employees may be tempted to cheat or steal, either in collusion or independently. For this reason, casinos invest a great deal of time, effort, and money into their security.