Colerain Township is a township in southeastern Lancaster County, Pennsylvania, United States. The population was 3,883 at the 2020 census, an increase over the figure of 3,635 tabulated in 2010. It is part of the Solanco School District.

Kirkwood is an unincorporated farming town and census-designated place (CDP) in Colerain Township, Lancaster County, Pennsylvania, United States. It is part of the Lancaster Metro area, in Pennsylvania Dutch Country. The ZIP code is 17536. As of the 2010 census, the population was 396.