Rheems is an unincorporated community and census-designated place (CDP) in Lancaster County, Pennsylvania, United States, between the boroughs of Elizabethtown and Mount Joy.

[4] It is mainly in West Donegal, but with the portion on the north side of Harrisburg Avenue lying in Mount Joy Township.

Lancaster, the county seat, is 16 miles (26 km) southeast of Rheems.

According to the United States Census Bureau, the CDP has a total area of 1.2 square miles (3.1 km2), of which 1.3 acres (5,432 m2), or 0.18%, are water.

Pierson Materials of NJ recently has been experiencing controversy about the expansion of their quarry into thirty acres of Rheems farmland.