Mystic Lake, lake of Stillwater County, Montana, United States of America

Mystic Lake is a reservoir in the Beartooth Mountains of Stillwater County, Montana, held back by a dam of the Montana Power Company. It is the second deepest lake in the Beartooth Range, after Deep Lake, and has the largest sandy beach in the Absaroka-Beartooth Wilderness. The lake lies at 2,340 m and supports a rainbow trout fishery.

Mystic Lake was enlarged for hydroelectric storage by the Montana Power Company, which dammed the lake outlet; the company's dam and power plant drew on its water. The lake lies at 2,340 m in Stillwater County and covers about 1.6 km², with Fish Creek and Huckleberry Creek nearby. It is the second deepest lake in the Beartooth Mountains after Deep Lake.

Mystic Lake holds rainbow trout, and anglers fish it today. The three-mile trail from the West Rosebud Valley trailhead climbs to the lake and passes views of the valley and other lakes. The lake has the largest sandy beach in the Absaroka-Beartooth Wilderness.

The lake is accessible from May through October, though the access road may be rough during shoulder seasons and parking is available at the trailhead. Bring plenty of water and hike early morning or late afternoon to avoid midday heat, especially over rocky sections where footing can be unreliable.

Mystic Lake holds the largest sandy beach in the Absaroka-Beartooth Wilderness, and it is the second-deepest lake in the Beartooth Mountains after Deep Lake. Montana Power Company uses the lake's water for power, and the reservoir supports a rainbow trout fishery. The three-mile trail up from West Rosebud Valley passes several other lakes.