Round Mountain is a small summit in southeastern Grand County, Utah, United States. It is located near the upper end of Castle Valley, Utah, about east-northeast of Moab. It rises above the valley floor in . Precipitation runoff from the mountain drains into Castle Creek, which is a tributary of the Colorado River. The nearest higher peak is Castleton Tower, to the north.
Round Mountain is made of gray hornblende plagioclase trachyte. It is sometimes called an extinct bysmalith, or igneous volcanic plug, but is more widely considered a shallow intrusion (laccolith) related to the La Sal Mountains immediately north.
Spring and fall are the most favorable seasons to visit Round Mountain. According to the Köppen climate classification system, it is located in a cold semi-arid climate zone with cold winters and hot summers. Summers highs rarely exceed . Summer nights are comfortably cool, and temperatures drop quickly after sunset. Winters are cold, but daytime highs are usually above freezing. Winter temperatures below are uncommon, though possible. This desert climate receives less than of annual rainfall, and snowfall is generally light during the winter.