De Borgia was named for the Saint Regis de Borgia River, by Father de Smet in 1841. Father de Smet was a member of the Jesuit order who founded the first Catholic mission, Saint Mary's Mission in Stevensville that same year. The first post office was established in 1900 with Elizabeth Wence as postmaster.
De Borgia is located in southwestern Montana, situated near the Idaho and Montana borders on I-90, just east of Saint Regis.