The Siege of Coimbatore was a siege conducted by forces of the Kingdom of Mysore against a garrison of British East India Company and Travancore troops holding the fortress at Coimbatore in southern India during the Third Anglo-Mysore War. The siege began in May 1791, and one attempt to storm the fort was repulsed on 11 June, after which the garrison of Lieutant Colonel John Chalmers was reinforced, and a larger Mysorean force was brought against it. The garrison eventually surrendered on 2 November. Tipu Sultan broke the terms of the surrender, and held the garrison's commanding officers prisoner.