a British chief, who fought against Caesar in his second campaign against Britain, B. C. 54.
He ruled over the country north of the river Tamesis (Thames), and as by his perpetual wars with his neighbours he had acquired the reputation of a great warrior, the Britons gave him the supreme command against the Romans.
After the Britons and Romans had fought in several engagements, the former abstained from attacking the Romans with their whole forces, which emboldened Caesar to march into the dominions of Cassivelaunus: he crossed the Thames, though its passage had been rendered almost impossible by artificial means, and put the enemy to flight; but he continued to be much harassed by the sallies of the Britons from their forests. The Trinobantes, however, with whom Cassivelaunus had been at war, and some other tribes submitted to the Romans. Through them Caesar became acquainted with the site of the capital of Cassivelaunus, which was not far off, and surrounded by forests and marshes. Caesar forthwith made an attack upon the place and took it. Cassivelaunus escaped, but as one or two attacks which he made on the naval camp of the Romans were unsuccessful, he sued for peace, which was granted to him on condition of his paying a yearly tribute and giving hostages. (Caes. Gal. 5.11
; D. C. 40.2
; Polyaen. Strat.
5; Beda, Eccles. Hist. Gent. Angl.