Horsetooth Reservoir (often known locally as Horsetooth) is a large reservoir in southern Larimer County, Colorado just west of the city of Fort Collins, Colorado. The reservoir sits in the foothills above the town on the western side of the Dakota Hogback, which contains the reservoir along its eastern side. The reservoir runs north-south for approximately 6.5 miles (10 km), and is approximately one-half mile (1 km) wide.
The reservoir is a popular recreation destination for the region. According to a recent study conducted by Reclamation and the recreation manager at Horsetooth, Larimer County Parks and Open Lands, approximately 570,000 visitors come to Horsetooth every year. Recreational boating is popular during summer months and swimming is allowed at the specifically designated Swim Beach maintained by LCPOL as well as in some of the coves. Kayaking and canoeing is also popular.