United Center is an indoor arena on the Near West Side of Chicago, Illinois, United States. It is home to the Chicago Bulls of the National Basketball Association (NBA) and the Chicago Blackhawks of the National Hockey League (NHL). It is named after its corporate sponsor United Airlines, which has been based in Chicago since 2007 and has a hub at O'Hare International Airport. With a capacity of nearly 21,000, the United Center is the largest arena by capacity in the NBA, and second largest arena by capacity in the NHL. It also has a seating capacity of 23,500 for concerts.