The Rocky Mountains lie to the east of the Great Basin, creating a natural boundary.

The Rocky Mountains form a major mountain range to the east of the Great Basin, extending from Canada through the western United States. These mountains play a key role in shaping the Great Basin's climate, creating a rain shadow effect. As moisture-laden air from the Pacific Ocean rises over the Rockies, it loses much of its moisture, leaving the Great Basin with arid conditions. The Rockies also serve as a physical boundary, separating the Great Basin from the Great Plains and influencing water flow into the region's rivers.