The Ellis Mounds are a complex of Native American mounds located near Marysville in Union County, Ohio, United States. These three mounds form an east-west line on a small ridgeline in a farm field. Believed to have been built by Hopewellian peoples, the mounds are important because they may reveal information about daily life in the Hopewell culture. While the mortuary customs of the Hopewell are well known, other aspects of their culture are little understood; consequently, a site with the potential of yielding information about such aspects is valuable indeed. Furthermore, the location of the mounds outside of the Hopewellian heartland farther south may demonstrate the spread of Hopewell influence.
In 1974, the archaeological significance of the Ellis Mounds was recognized when they were listed on the National Register of Historic Places.