Headquarters: Reno, Nevada, United StatesĬaesars Entertainment is one of the largest gambling companies online and in retail.We have reviewed each across several key criteria to present you with a quick, up-to-date reference. You will find a list of listed gambling companies and operators that are considered the largest entities in the industry across Europe, the United Kingdom, the USA, and beyond. Today, we take a look at the biggest online gambling companies and physical operators. This helps keep the industry vibrant and in check, giving gambling brands an extra incentive to compete for market share. The world of gambling is full of competition and rivalries.