| Guernsey Dam | |
| Location Map: | Wyoming#USA |
| Location Map Caption: | Location of Guernsey Dam in Wyoming |
| Coordinates: | 42.2902°N -104.7637°W |
| Dam Crosses: | North Platte River |
| Res Name: | Guernsey Reservoir |
| Location: | Platte County, Wyoming, USA |
| Operator: | U.S. Bureau of Reclamation |
| Dam Length: | 560feet[1] |
| Dam Height: | 135feet |
| Construction Began: | 1925[2] |
| Opening: | 1928 |
Guernsey Dam is an earthfill dam on the North Platte River in Platte County in the U.S. State of Wyoming. The dam creates Guernsey Reservoir, the last of the 5 major reservoirs on the North Platte River in Wyoming. The dam contains a hydroelectric plant capable of 6.4 megawatts of electricity. The total capacity of the reservoir is of water which is used mainly for irrigation. Morrison-Knudsen (Now URS Corporation) and Utah Construction Company constructed Guernsey Dam and the hydroelectric plant as part of the North Platte Project to provide irrigation to eastern Wyoming and western Nebraska. Guernsey helps control the river flow and stores water released from the project's primary storage upstream at Pathfinder Reservoir. About 8miles downstream of the dam the Whalen Diversion Dam diverts water into the Fort Laramie and Interstate Canals that service farms in Wyoming and Nebraska.
The reservoir is surrounded by Guernsey State Park.