Oneco is an unincorporated community in Manatee County, Florida, United States. It is a suburb of Bradenton, located just southeast of the city. The community is part of the Bradenton–Sarasota–Venice Metropolitan Statistical Area. In the 1920 Census it was enumerated as Precinct 6. The community reported as a Census-designated place by the U.S. Census Bureau from 1960 to 1980.
A post office has been in operation at Oneco since 1889. The origin of the name Oneco is unclear. Some say it was the name of a Mahican Indian, while others believe the community was so named from the fact it was once a one-company ("one co.") town.