Medocius (Mars Medocius) is a Brythonic god known from a single inscription found at Colchester, England where he is equated with Roman Mars. He appears to be a battle god, equivalent to the martial aspect of Roman Mars.

Medocius is a deity known from Camulodunon, Colchester, Essex where he is assimilated by interpretato Romana with the Roman deity Mars. The inscription itself (RIB 0191) reads: DEO MARTI MEDOCIO CAMPESIVM ET VICTORIE ALEXANDRI PII FELICIS AVGVSTI NOSI DONVM LOSSIO VEDA DE SVO POSVIT NEPOS VEPOGENI CALEDO (To the god of the battlefields Mars Medocius, and to the victory of [Imperator Caesar Marcus Aurelius Severus] Alexander Pius Felix Augustus, Lossius Veda the grandson of Vepogenus Caledos, placed [this] offering out of his own [funds]). As the Colchester garison was home to a detachment of Libyan infantry some have proposed that Medocius was a Libyan deity. However, his name could just as easily be derived from the reconstructed proto-Celtic roots *medwo-oci- (he who is drunk, drunkard) along with the lexeme *okitā- (to harrow) and yields something like ‘Mead-harrower’.

In this respect the deity’s assimilation with the cult of Mars is of note, especially as the inscription indicates that this assimilation was in a martial capacity. Indeed, it is well attested that deities such as: Dyfed, Brâg/Braciaca. Latis and the Irish deity Maev, which are all gods named after beer/drunkenness/intoxication and are indicative of the Celtic parctice of getting drunk before battle. In Celtic terms, therefore, a battle deity is a god/goddess of intoxication and the assimilation of Medocius into the cult of Mars makes sense. In the inscription his consort is given as the Roman goddess Victory and Mediocus’ name ‘Mead-harrower’ could be interpreted as ‘War-harrower’, using the Celtic link between mead and the battle deity. As such he would be a fitting consort for the goddess of victory.