Lake San Cristobal, Mountain lake in Hinsdale County, United States.

Lake San Cristobal is a freshwater lake in the San Juan Mountains of Hinsdale County, Colorado, at 9,003 feet (2,744 m) elevation. It is 2.1 miles (3.4 km) long, up to 89 feet (27 m) deep, covers 0.52 square miles (1.3 km²), and holds about 11,000 acre-feet of water. The lake stretches north to south, with a small 70-by-40-metre island in its western part connected to shore by a narrow bridge; the southern shore is marshy, while the other shores are hilly and steep.

The lake formed roughly 700 years ago when a massive landslide called the Slumgullion Earthflow created a natural dam across the Lake Fork of the Gunnison River. This geological event shaped the landscape into the basin that exists today.

The name San Cristóbal is Spanish for Saint Christopher. Lake City, the only town in Hinsdale County, takes its name from the lake. Anglers come for the Rainbow Trout stocked in the water, and several recreation areas line the shores.

Roads 30 and 33 run along all the lake shores, and a small island in the western part, about 70 by 40 metres, is joined to the bank by a narrow bridge. The southern shore is marshy, while the other banks are hilly and steep. Water levels are adjusted by adding or removing boulders at the outlet.

The lake maintains its stability because its foundation is made of non-porous material that holds water rather than allowing it to drain away. A natural spillway carved into bedrock allows excess water to overflow safely, which is why this body of water has persisted for centuries.