Otter Tail Corporation is an electric power and manufacturing company based in Fergus Falls, Minnesota.

The company currently has a workforce of over 750 employees, a generating capacity of 660 megawatts, and owns over 5,000 miles (8,000 km) of electrical power transmission lines (the majority of which are operated at 41.6 kV).

The company was incorporated in 1907 when funds were secured to begin construction of the Dayton Hollow Dam southwest of Fergus Falls.

Shortly thereafter, contracts were secured to provide power at wholesale to the cities of Breckenridge and Fergus Falls, MN (the latter after their own municipal utility's dam failed).

Northern Light Electric also merged with Otter Tail at this time and its owner came on board as the company's first general manager.

The one exception in this territory is the Red River Valley between Grand Forks and Fargo, ND, which was then and still is served by Northern States Power Company (now Xcel Energy).

By the 1990s, flat revenues from the utility operations led the company to establish a subsidiary (Varistar) to acquire and oversee non-utility businesses.

Hoot Lake is unique in that the dam also formed the water intake for the coal-fired power plant that once stood nearby.

At the time of its retirement and demolition in 2021 (as part of Minnesota's commitment to carbon-free sources of energy), only the two most recent units (built in 1959 and 1964) were still in operation.