Lucas de Tui (or O Tudense) (died 1249) was a Leonese cleric and intellectual, remembered best as a historian.
In 1233 or 1234 he passed Easter in Rome and completed his tract De altera vita fideique controversiis adversus Albigensium errores against the Cathars, taking inspiration mainly from Isidore and Jerome.
In 1236, upon a request from Queen Berenguela, he composed the Chronicon mundi, a four-part chronicle of world history and his magnum opus.
Beginning with Creation and ending in 1236, the Chronicon aspired to give comprehensive coverage to two topics: the world and the Spains.
Lucas' principal sources are Isidore, John of Biclar, Hydatius, Orosius, the Chronicle of Alfonso III, the Crónica Silense, and Sampiro.