The Ordovices were one of the Celtic tribes living in Great Britain before the Roman invasion. Their tribal lands were located in present-day North Wales and England, between the Silures to the south and the Deceangli to the north-east. Unlike the latter tribes that appear to have acquiesced to Roman rule with little resistance, the Ordovices fiercely resisted the Romans. They were eventually subjugated by the Roman governor Gnaeus Julius Agricola in the campaign of 77–78CE when the Romans overran their final strongholds on Anglesey.
The Celtic name *ordo-wik- could be cognate with the words for 'hammer': Irish: ord, Welsh: gordd (with a prothetic g-) and Breton: horzh (with a prothetic h-). The name of this tribe appears to be preserved in the place name Dinorwig ("Fort of the Ordovices") in North Wales.
In 1879 the pioneering English geologist Charles Lapworth named the Ordovician geological period after the Ordovices because of the rocks he was studying were found in the tribe's former territories in North Wales.
The Ordovices farmed and kept sheep, and built fortified strongholds and hill forts. They were among the few British tribes that resisted the Roman invasion. The resistance was mainly organised by the Celtic leader Caratacus, exiled in their lands after the defeat of his tribe in the Battle of the Medway. Caratacus became the warlord of the Ordovices and neighbouring Silures, and was declared a Roman public enemy in the 50s AD. Following the Battle of Caer Caradoc, where governor Publius Ostorius Scapula defeated Caratacus, the Ordovices were no longer a threat to Rome, probably due to heavy losses.
In the 70s, the Ordovices rebelled against Roman occupation and destroyed a cavalry squadron. This act of war provoked an equally strong response from Agricola, who, according to Tacitus, invaded Anglesey and went on to exterminate almost the whole tribe. No other mention of the tribe appears in the historical records, but in view of the mountainous terrain of the lands of the Ordovices, it is questionable whether Agricola could have killed the entire population.
- Agricola c. 18, caesaque prope universa gente, "with almost the whole tribe having been cut down"