24 Hour Fitness is a privately owned and operated fitness center chain headquartered in San Ramon, California. It is the world's largest fitness chain based on memberships and the third in number of clubs behind Gold's Gym and Fitness First. The company operates over 400 clubs in 13 states in the US and serves nearly 4 million members. 24 Hour Fitness offers a variety of fitness equipment, group exercise classes, personal and group training, and other services. The company was founded in 1983 and is owned by AEA Investors and the Ontario Teachers' Pension Plan.