Although some sources say that gambling sites were popular among the Romans, Greeks and Chinese, and that they had coin-operated slot machines, there is no clear answer as to who built the first casino. Some researchers also think that casinos may have existed in one form or another as early as 5000 BC.

The first known European gambling house, not called a casino although meeting the modern definition, was the Ridotto, established in Venice, Italy, in 1638 by the Great Council of Venice to provide controlled gambling during the carnival season.