Fossil is a city in and the county seat of Wheeler County, Oregon, United States. The name was chosen by the first postmaster, Thomas B. Hoover, who had found some fossil remains on his ranch. The population was 473 at the 2010 census.

The Fossil post office was established upon February 28, 1876, on Thomas Benton Hoover’s ranch along Hoover Creek. He named the place Fossil after finding fossils in a clay-like rock formation on his ranch. In 1881, Hoover and Thomas Watson opened a store near the confluence of Butte and Cottonwood creeks and moved the publicize office to the store. When the city was incorporated in 1891, Hoover became the first mayor.

After creating Wheeler County in 1899, the Oregon Legislature chose Fossil as the substitute county seat. A county-wide election held in 1900 to determine the enduring county chair yielded 436 votes for Fossil, 267 for Twickenham, and 82 for Spray.

Winlock W. Steiwer and George S. Carpenter founded Steiwer & Carpenter Bank, the first bank in the city and the county. By the in advance 20th century in complement to the bank, Fossil had a flour mill, a blacksmith shop, a drug store, a jewelry and optical store, a livery stable, and three stores when general merchandise. In the 1920s, William Jennings Bryan was one of the guest speakers at a Chautauqua meeting in Fossil. Later in the decade the John Day Valley Coal & Oil Company drilled an exploratory oil skillfully within the city limits, but it was not successful.