Hosmer is a city in Edmunds County, South Dakota, United States. The population was 208 at the 2010 census.
Hosmer was founded by Russian citizens of German descent. They settled shortly after the townsite of Hosmer was platted by a surveyor for the Chicago, Milwaukee, St. Paul & Pacific Railroad. The official date of platting was April 29, 1887. Hosmer is well known for its Germans from Russia peoples. Hosmer has traditionally been a farming community.
The name for the town of Hosmer came from a railroad agent's wife's maiden name, Stella A. Hosmer.