Ogallah is a census-designated place (CDP) in Trego County, Kansas, United States. As of the 2020 census, the population was 28. It is located approximately 7 miles east of WaKeeney.
Ogallah was named for the Oglala Lakota tribe.
The post office was established January 27, 1879.
The climate in this area is characterized by hot, humid summers and generally mild to cool winters. According to the Köppen Climate Classification system, Ogallah has a humid subtropical climate, abbreviated "Cfa" on climate maps.