Coaticook is a town on the Coaticook River, located in southeastern Quebec, Canada. It resides in the region of Estrie, which is often referred to colloqually as the Eastern Townships. It is the seat of the Coaticook Regional County Municipality, and its southern border is also the Canada–United States border. The town of Coaticook was initially settled in the 1820s by British Loyalists coming from New England.