The 2017–18 Mohun Bagan A.C. season is the 128th season of Mohun Bagan A.C. since the club's formation in 1889 and their 11th season in the I-League which is India's top football league. They finished 2nd in the table in the Calcutta Football League and finished 3rd in the I-League. Sanjoy Sen resigned as the coach of Mohun Bagan on 2 January 2018 following three home draws and a defeat against Chennai City placing the team in 4th position, virtually ending their title hopes. Shankarlal Chakraborthy was appointed as head coach for the remainder of the season.