ATK Mohun Bagan FC is an Indian professional football club based in Kolkata, West Bengal. The club competes in Indian Super League, the top flight of Indian football. Their reserve side most often competes in Calcutta Football League. The club, which was formed as a merger between the football section of multi-sport club Mohun Bagan AC and the ATK FC, began to play from the 2020-21 season as ATK Mohun Bagan FC. The entity continues with the existing registration of Mohun Bagan AC with RIFF and IFA (W.B.), and its history and tradition.