| Surprise Valley, Modoc County | |
|---|---|
 | |
| Length | 60 mi (97 km) |
| Geography | |
| Location | Modoc County, California |
| Population centers | Cedarville, Lake City, Fort Bidwell, Lake Annie, Eagleville |
| Borders on | Warner Mountains-NW, W & SW Hays Canyon Range-E & SE |
| Coordinates | 41°31′45″N 120°10′24″W / 41.52917°N 120.17333°W |
Surprise Valley is an endorheic valley in extreme northeastern California, about 60 miles in length from north to south. Locals refer to the area as the Tricorner Region because of the region's location at the intersection of California, Oregon, and Nevada state lines. The valley is east of the Modoc County seat of Alturas. The area is part of the Great Basin which extends across most of the northern half of Nevada.