The Henry Mountains is a mountain range located in the southeastern portion of the U.S. state of Utah that runs in a generally north-south direction, extending over a distance of about 30 miles (48 km). They were named by Almon Thompson in honor of Joseph Henry, the first secretary of the Smithsonian Institution. The nearest town of any size is Hanksville, Utah, which is north of the mountains. The Henry Mountains were the last mountain range to be added to the map of the 48 contiguous U.S. states (1872), and before their official naming by Thompson were sometimes referred to as the "Unknown Mountains." In Navajo, the range is still referred to as Dził Bizhiʼ Ádiní.

Almon Harris Thompson, also known as A. H. Thompson, was an American topographer, geologist, explorer, educator and Civil War veteran. Often called "The Professor" or simply "Prof", Thompson is perhaps best known for being second in command of John Wesley Powell's Second Geographical Expedition (1871–1875), a federally funded scientific expedition that retraced the route of Powell's original expedition in order to further explore and map the drainages and canyons of the Green and Colorado Rivers in what is now southern Utah and northern Arizona. Thompson's diary of the expedition was originally published in the Utah Historical Quarterly in 1939. Through his work on the Powell expeditions and later as a geographer at the U.S. Geological Survey, he was responsible for naming many geographic locations in the Western United States. Thompson is also known for being a founding member of the National Geographic Society.