ROUSSILLON, formerly a French province, now comprised in the department of Pyrenees Orientales (q.v.). It was bounded S. by the Pyrenees, W. by the county of Foix, N. by Languedoc and E. by the Mediterranean. The province derived its name from a small place near Perpignan, the capital, called Ruscino (Rosceliona, Castel Rossello). It formed part of the Roman province of Gallia Narbonensis until in the 5th century it was ceded with the rest of Septimania to Theodoric II., king of the Visigoths. It has little distinctive history until the appearance of a line of hereditary counts late in the 9th century. The district does not seem to have formed a single lordship before the i 2th century, when it passed under the rule of the counts of Barcelona and their successors, the kings of Aragon. Under the Aragonese monarchs the province was prosperous, and Collioure, the port of Perpignan, became a centre of Mediterranean trade. By the
treaty of Corbeil (1258) Louis IX. surrendered the sovereignty of Roussillon and the ancient countship of Barcelona to Aragon, and from that time until the 17th century the province ceased to belong to France. In the first half of the 17th century the decay of Spain was France's opportunity, and on the revolt of the Catalans against the Castilians in 1641, Louis XIII. supported the former, and the treaty of the Pyrenees in 1659 secured Roussillon to the French crown.