Dennis is an unincorporated community in Parker County, Texas, United States. Its elevation is 728 feet (222 m). Although Dennis is unincorporated, it has a post office, with the ZIP code of 76439.N. M. Dennis, a local judge, founded the community at the spot of a bridge across the Brazos River in 1892. The community's post office was opened in 1895. Today, FM 1543 passes through the community.As of the 2000 census the town has 90 residents.