Hamilton Township, one of the eleven townships of Warren County, Ohio, United States, is in the south central portion of the county. The 2000 census found 9,630 people there, up significantly from the 5,900 in 1990. 8,645 of the total in 2000 lived in the unincorporated portions of the township. It is the fastest growing area of Warren County and is about 36 miles² (93 km2) in area.