The Centennial Mountains are the southernmost sub-range of the Bitterroot Range in the United States states of Idaho and Montana. The Centennial Mountains include the Western and Eastern Centennial Mountains. The range extends east from Monida Pass along the Continental Divide to Henrys Fork NNW of Ashton, Idaho; bounded on the west by Beaver Creek, on the north by Centennial Valley and Henrys Lake Mountains, on the east by Henrys Lake Flat, and on the south by Shotgun Valley and the Snake River Plain. The highest peak in the range is Mount Jefferson.