Big Plain is an unincorporated community in Fairfield Township, Madison County, Ohio, United States.

[2] The community was originally laid out by Thomas Chappel, Robert Thomas and William D. Pringle in the spring of 1849, and was then named California, after the recent gold rush in the state of the same name,[3] and the community was later expanded by Pringle.

[4] As of 1875, the community had one church, two dry goods stores, one drug store, two blacksmith and wagon shops, two physicians, and one shoe shop.

[4] Due to there already being a post office named California elsewhere in the state, the Big Plain Post Office was established on June 17, 1850,[5] named after large prairies in the area known as the "Big Plains".

[5] As of 1915, the community contained a church, a Knights of Pythias lodge, and the township hall.