Castor is a village in Bienville Parish in north Louisiana, United States. The population was 209 at the 2000 census but increased 23% to 258 in 2010. The median age was 32.2 years. The village was established in 1900. The name "Castor" refers to the genus Castoridae or beaver, a Latin term, contrary to an oral tradition of the word being Native American in origin.

Bienville Parish is a parish located in the northwestern portion of the U.S. state of Louisiana. At the 2020 census, the population was 12,981. The parish seat and most populous municipality is Arcadia.