Adin (formerly, Adinville and Aidenville) is a census-designated place in Modoc County, California. It is located 29 miles (47 km) southwest of Alturas, at an elevation of 4203 feet (1281 m). The population was 272 at the 2010 census.
Adin, the first town in Modoc county west of the Warner Mountains, was founded in 1869 by Adin McDowell as the supply point for the mining town of Hayden in northern Lassen County, and was named for him in 1870. The Aidenville post office opened in 1871, and changed its name to Adin in 1876.
A 1913 book described Adin as having a population of 200, and as the chief town of the Big Valley. It became a sawmill town in the mid-1930s when the Edgerton Brothers Mill moved into town, from the Adin Mountains.