It is the capital of the district Kelheim and is situated at the confluence of the rivers Altmühl and Danube.

Kelheim is the site of a large Iron Age oppidum from the La Tène period, which has been tentatively identified with the Celtic city of Alcimoennis mentioned by Ptolemy in his Geography.

A small promontory fort on the other bank of the Danube has a series of short linear ramparts protecting a settlement in the bend of a meander.

Kelheim has given its name to the pfostenschlitzmauer style of rampart construction characterized by vertical wooden posts set into the stone facing.

According to tradition of Braunau in Rohr Abbey, Kelheim received borough rights in 1151.