The Battle of Crogen is an engagement said to have taken place in Wales during Henry II of England's summer 1165 campaign against an alliance of Welsh princedoms led by Owain Gwynedd.

It is unclear whether events in the Ceiriog Valley represented a pitched battle, a series of smaller engagements or a minor skirmish: all three have been argued, as well as the possibility no fighting took place during the 1165 campaign.

Henry II began planning a punitive campaign into Wales in 1164, ostensibly to take action against several Welsh princes, particularly Rhys ap Gruffudd of Deheubarth, who had been responsible for disturbances along the border in breach of the 1163 settlement.

[3] Welsh chronicles of the time argued that Henry's Marcher Lords, particularly Roger de Clare, 2nd Earl of Hertford, had themselves failed to keep to the terms of the agreement.

During the summer of 1165 he assembled a substantial force at Shrewsbury, including troops from England and mercenaries from the Continent: several contemporary chronicles emphasised the large size of the Angevin army.

Some modern sources repeat a story that Hubert de St Clare, the Constable of Colchester Castle, sacrificed his own life when he threw himself in front of an arrow meant for Henry.

Undeterred by their losses in the Ceiriog Valley, Henry's army continued into the Berwyns, possibly making for Corwen via a pass still known as the "English Road" (Ffordd y Saeson).

[3] He then moved his army to Chester: the Welsh annals claimed that this was in order to wait for a fleet from Dublin, with whose rulers Henry had recently entered into a treaty,[16] but rather than continuing his campaign he abandoned the plan completely and returned to his court at Anjou.

[3] Despite this, he was back on good terms with the princes of Powys within a year; both Owain Cyfeiliog and Iorwerth Goch were in friendly contact with Henry's court within months.

[17] It has been suggested that Henry's lack of support for the marcher barons after 1165 ultimately encouraged them to seek lands and opportunities elsewhere, contributing substantially to the subsequent Norman invasion of Ireland.