Legio XX Valeria Victrix ("victorious black eagle"?) was a Roman legion, probably raised by Augustus sometime after 31 BC. It served in Spain, Illyricum, and Germany before participating in the invasion of Britain in 43 AD, where it remained and was active until at least the beginning of the 4th century. The emblem of the legion was a boar.
XX Valeria Victrix was part of the great army that campaigned against the Cantabrians in Hispania Tarraconensis from 25 to 13 BC. The legion then moved to Illyricum, and is recorded in the army of Tiberius operating against the Marcomanni in 6 AD. In one battle the legion cut through the enemy lines, was surrounded, and cut its way out again.
The legion was one of the four with which Claudius invaded Britain in 43, after which it encamped at Colchester (Camulodunum), with some units at Kingsholm in Gloucester. In 60 it helped put down the revolt of Queen Boudicca.
In the year of the four emperors, the legion sided with Vitellius, some units going with him to Rome. In 78-84, it was part of Agricola's campaigns in northern Britain and Scotland, and built the base at Inchtuthil that they occupied until returning south in 88 and occupying Chester, where it remained for at least two centuries.
This legion has been much studied; at least 250 members of the legion have been identified in surviving inscriptions.