Gallatin Gateway is a census-designated place in Gallatin County, Montana, United States. As of the 2010 census it had a population of 856. Elevation is 4,953 ft. The community is located along U.S. Route 191 in the valley of the Gallatin River, a north-flowing tributary of the Missouri River. US 191 leads north, then east 13 miles to Bozeman and south 28 miles to Big Sky. According to the U.S. Census Bureau, the CDP has a total area of 5.9 square miles, of which 5.8 square miles is land and 0.1 square miles, or 1.83%, is water.