The Green River, located in the western United States, is the chief tributary of the Colorado River. The watershed of the river, known as the Green River Basin, covers parts of Wyoming, Utah, and Colorado. The Green River is long, beginning in the Wind River Mountains of Wyoming and flowing through Wyoming and Utah for most of its course, except for into western Colorado. Much of the route is through the Colorado Plateau and through some of the most spectacular canyons in the United States. It is only slightly smaller than the Colorado when the two rivers merge, but typically carries a larger load of silt. The average yearly mean flow of the river at Green River, Utah is per second.

Green River is a city in Emery County, Utah, United States. The population was 1,132 at the 2010 census.