James I the Conqueror (Catalan: Jaume el Conqueridor, Aragonese: Chaime lo Conqueridor, Spanish: Jaime el Conquistador, Occitan: Jacme lo Conquistaire; 2 February 1208 – 27 July 1276) is the King of Aragon, Count of Barcelona, and Lord of Montpellier from 1213 to 1276.

His long reign sees the expansion of the Crown of Aragon on all sides: into Valencia to the south, Languedoc to the north, and the Balearic Islands to the east.

By a treaty with Louis IX of France, he wrests the county of Barcelona from nominal French suzerainty and integrates it into his crown.

His part in the Reconquista is similar in Mediterranean Spain to that of his contemporary Ferdinand III of Castile in Andalusia.

As a legislator and organizer, he occupies a high place among the Spanish kings.

James compiles the Llibre del Consulat de Mar, which govers maritime trade and helps establish Catalan-Aragonese supremacy in the western Mediterranean.

He is an important figure in the development of Catalan, sponsoring Catalan literature and writing a quasi-autobiographical chronicle of his reign: the Llibre dels fets.