A casino is an establishment for certain types of gambling. Casinos are often built near or combined with hotels, resorts, restaurants, retail shops, and cruise ships. They provide gambling facilities for customers and are usually open 24 hours a day. Casinos can be highly profitable, making billions in profits each year for companies, investors, and Native American tribes. They also generate significant revenue from tourists and local residents.

In the twenty-first century, casinos are increasingly focusing on high-stakes gamblers, offering them luxuries such as free suites and personal attention. Casinos have a wide range of games that can be played with money or paper tickets, including craps, roulette, and poker. Most casino games are based on luck, but some have an element of skill (e.g. blackjack). The odds of winning or losing are mathematically determined by the rules of the game. The house always has a mathematical advantage over players, which is called the house edge or expected value. In games that involve skill, the house may make additional revenue by taking a percentage of each wager or through a commission on the sale of items to gamblers.

The first casino opened in the elegant spa town of Baden-Baden about 150 years ago, drawing royalty and aristocracy from across Europe. In the early twentieth century, European countries liberalized their laws to permit casinos. In America, they began appearing on Atlantic City beaches and in riverboats, as well as on American Indian reservations that were excluded from state antigambling laws.