ATREBATII, a people of Britain, who inhabited part of Berkshire and Oxfordshire, next to the Bibroci. This was one of those Belgic colonies which came out of Gaul into Britain, and there retained their ancient name. They are mentioned by Cæsar among the nations which composed the Belgic confederacy against him; and the quota of troops which they engaged to furnish on the occasion to which he refers was 15,000. Comius of Arras was a king or chieftain among the Atrebatii of Gaul in Cæsar's time; and he seems to have possessed some influence over the Atrebatii of Britain, for he was sent by Cæsar to persuade them to submission. This circumstance renders it probable that this colony of the Atrebatii had not been settled in Britain very long before that time. The Atrebatii were amongst the British tribes which submitted to Cæsar; nor do we hear of any remarkable resistance they made against the Romans at their next invasion under Claudius. It is indeed probable that, before the time of this second invasion, they had been subdued by some of the neighbouring states; perhaps by the powerful nation of the Catuvellauni; which may also be the reason why they are so little mentioned in history. Calliva Atrebatum, mentioned in the seventh, twelfth, thirteenth, and fourteenth Itineraria of Antoninus, and called by Ptolemy Calcula, seems to have been the capital of the Atrebatii. But our antiquaries differ respecting the situation of this ancient city; some of them placing it at Wallingford, and others at Ilchester.