Altus () is a city and the county seat in Jackson County, Oklahoma, United States. The population was 19,813 at the 2010 census, a loss of 7.7 percent compared to 21,454 at the 2000 census.
Altus is home to Altus Air Force Base, the United States Air Force training base for C-17, KC-46 and KC-135 aircrews. It is also home to Western Oklahoma State College and Southwest Technology Center.
The town that would later be named Altus was founded in 1886. The community was originally called "Frazer", a settlement of about 50 people on Bitter Creek that served as a trading post on the Great Western Cattle Trail. Cowboys driving herds northward often stopped to buy buttermilk from John McClearan. Thus, the town was known locally as "Buttermilk Station". The Frazer post office opened February 18, 1886. A flash flood nearly destroyed Frazer on June 4, 1891. The residents moved to higher ground 2.5 miles (4.0 km) east of the original site.