The Grand Valley is an extended populated valley, approximately 30 miles (48 km) long and 5 miles (8.0 km) wide, located along the Colorado River in Mesa County in western Colorado and Grand County in eastern Utah in the Western United States. The valley contains the city of Grand Junction, as well as other smaller communities such as Fruita and Palisade. The valley is a major fruit-growing region that contains many orchards and vineyards, and is home to one of two designated American Viticultural Areas in Colorado: the Grand Valley AVA. It takes its name from the "Grand River", the historical name of the Colorado River upstream from its confluence with the Green River that was used by locals in the late 19th and early 20th century. The valley is the most densely populated area on the Colorado Western Slope, with Grand Junction serving as an unofficial capital of the region, as a counterpoint to Denver on the eastern slope of the Rocky Mountains in the Colorado Front Range. Interstate 70 and U.S. Highway 6 run through the valley from west-to-east. The Grand Valley is part of the larger Colorado Plateau desert lands.

The Western Slope is a colloquial term generally understood to describe the part of the state of Colorado west of the Continental Divide. Bodies of water west of the Divide flow toward the Pacific Ocean; water that falls and flows east of the Divide heads east toward the Gulf of Mexico. The Western Slope encompasses about 33% of the state, but has just 10% of the state's residents. The eastern part of the state, including the San Luis Valley and the Front Range, is the more populous portion of the state.