The Battle of Cirencester was fought in 628 at Cirencester in modern-day England. The conflict involved the armies of Mercia, under King Penda, and the Gewisse (predecessors of the West Saxons), under Kings Cynegils and Cwichelm.

The Anglo-Saxon Chronicle (A) states:

628. Here Cynegils and Cwichelm fought against Penda at Cirencester, and then came to an agreement.

This suggests that the Gewisse were defeated.

Cirencester had nominally been under the influence of the Gewisse since Battle of Dyrham in 577, although archaeological evidence suggests Anglo-Saxon settlement near the Roman town from the mid sixth century. Henceforward the region would be controlled by the minor kingdom of the Hwicce.