Almon Harris Thompson (September 24, 1839 – July 31, 1906), also known as "A. H. Thompson", was an educator, topographer, geologist, explorer, and Civil War veteran. Often called "The Professor" or simply "Prof", Thompson was second in command of John Wesley Powell's Second Expedition, a federally-funded expedition to explore the Green and Colorado Rivers, Colorado drainage and canyons, and map southern Utah and northern Arizona. Thompson's diary of Powell's Second Expedition (1871–1875) was originally published in the Utah Historical Quarterly in 1939. Through his work on the Powell expeditions and later as geographer at the US Geological Survey, he was responsible for naming many geographic locations in the west. Thompson is also known for his involvement in the formation of the National