The Roman Empire suffered great upheavals and changes during the third and fourth centuries. The borders became insecure and there were repeated economic and social crises. Christianity, a new monotheistic religion of Judaic origin, displaced traditional beliefs. Initially, the new cult was repressed but in 313 the Emperor Constantine legalised its practice and Christianity was subsequently established as the official state religion by Theodosius I.

The Christians' solid hierarchical organisation made the Church one of the main supports of the teetering Empire. Various Germanic peoples settled within the Empire, which finally collapsed in 476. The Visigoths, who dominated the south of Gaul, moved into Hispania. The province of Tarragona remained loyal to Rome to the end and Roman cultural characteristics were maintained, in spite of the constitution of the Visigoth kingdom of Toledo.