The Silures were a powerful and warlike tribe of ancient Britain, occupying approximately the counties of Monmouth, Brecon and Glamorgan.

They made a fierce resistance to the Roman conquest about AD 48, with the assistance of Caratacus, a military leader and prince of the Catuvellauni, who had fled from further west after his own tribe was defeated.

To aid the Roman administration in keeping down local opposition, a legionary fortress (Isca Silurum, Caerleon) was planted in the midst of tribal territory, and by AD 78 they were overcome. Their town Venta Silurum (Caerwent, 6 miles west of Chepstow) became a Romanized town, not unlike Silchester, but smaller. Its massive Roman walls still survive, and excavations have revealed a forum, a temple, baths, amphitheatre, shops, and many comfortable houses with mosaics, etc. An inscription shows that under the Roman Empire it was the capital of the Silures, whose ordo or county council provided for the local government of the district.

Reference is occasionally made to this period of Celtic history by the use of made-up terms such as "Silurian". The poet, Henry Vaughan, called himself a "Silurist", by virtue of his South Walean roots.

The geologic period Silurian was first described by Roderick Murchison in rocks located in the original lands of the Silures, hence the name.