It is about seven kilometres (4+1⁄2 miles) south of Heidelberg and the third largest town of the Rhein-Neckar district after Weinheim and Sinsheim.

Leimen is located on the Bergstraße (Mountain Road) and on the Bertha Benz Memorial Route.

When Leimen's population exceeded 20,000 in 1990, the city council applied for elevation to a Große Kreisstadt which was granted by the state government on 1 April 1992.

The first documentary record of Leimen is from 791, when both the Lorsch Abbey and the Diocese of Worms owned land there.

First records of the districts are from 1270 for Gauangelloch (a document supposedly from 1016 was found out to be a fake), 1312 for Lingental, around 1300 for Ochsenbach and 1100 for Sankt Ilgen, then called bruch, an Old High German word for bog.