The Great Basin is a desert area in the western United States of America, part of the Basin and Range Province. It is very dry and very large, occupying most of the state of Nevada and extending into California, Idaho, Oregon, Utah, and a small part of Wyoming. In all, is about 200,000 square miles (520,000 square kilometers) in size. It is an 'endorheic' basin, which means that there is no outlet to the ocean. The Great Basin runs from the highest land in the Sierras and Rockies in the west, down to lowland deserts in the east.
The Great Basin's longest and largest river is the Bear River of 350 mi (560 km), and the largest single watershed is the Humboldt River drainage of roughly 17,000 sq mi (44,000 km2).
Most Great Basin precipitation is snow. The water that neither evaporates nor is taken for human use will sink into groundwater aquifers. Evaporation occurs from geographic sinks.
Lake Tahoe, North America's largest alpine lake, is part of the Great Basin's central Lahontan subregion.