Gustavus Loomis (1789–1872) was an American breveted Brigadier General who served during the Indian wars and the American Civil War.
Loomis was born in 1789 in Thetford, Vermont and graduated from West Point in 1811.
He entered the army as a second lieutenant of artillery. After garrison duty in the harbor of New York in 1812-13, he was ordered to the Niagara frontier in 1813. He assisted in the capture of Fort George (May 27, 1813) and was made prisoner at Fort Niagara on December 19. In 1832-33, during the Black Hawk War, he was in garrison at Fort Crawford, Wisconsin, in 1837, in 1852-53 commanded the 5th Infantry Regiment at Fort Belknap, TX, in 1856-58 served against the Seminole Indians, and in 1857-58 commanded the Department of Florida. During the Civil War he was superintendent of the general recruiting services, and in 1863 was retired from active service with rank of colonel of infantry. In 1865 he was appointed a brevet brigadier general for long and faithful service in the army.