Thomas Basin (1412–1491) was a French bishop of Lisieux and historian.
Basin was born probably at Caudebec in Normandy, but in the devastation caused by the Hundred Years' War, his childhood was itinerant.
In 1424 Basin went to the University of Paris, where he became a master of arts in 1429 and afterward studied law at Leuven and Pavia. He attended the Council of Florence and was soon made canon of the church at Rouen, professor of canon law in the new university of Caen and vicar-general for the bishop of Bayeux. In 1447 he became bishop of Lisieux.
Basin was much involved in the wars between the English and French and was employed by Charles VII of France and by his successor Louis XI, at whose request Basin drew up a memorandum setting forth the misery of the people and suggesting measures for alleviating their condition. In 1464 the bishop joined the League of the Public Weal and fell into disfavour with the king, who seized the temporalities of his see. After exile in various places Basin proceeded to Rome and renounced his bishopric. At this time (1474) Pope Sixtus IV bestowed upon him the title of archbishop of Caesarea. Occupied with his writings Basin then passed some years at Trier and afterwards transferred his residence to Utrecht (now in the Netherlands), where he died on 3 December 1491. He was buried in the church of St. John, Utrecht.
Basin's principal work is his Historiae de rebus a Carolo VII. et Ludovico XI. Francorum regibus. This is of considerable historical value, but is marred to some extent by the author's dislike for Louis XI. At one time it was regarded as the work of a priest of Liege, named Amelgard, but it is now practically certain that Basin was the writer. He also wrote a suggestion for reform in the administration of justice entitled Libellus de optimo ordine forenses lites audiendi et deferendi; an Apologia, written to answer the charges brought against him by Louis XI; a Breviloquium, or allegorical account of his own misfortunes; a Peregrinatio; a defence of Joan of Arc entitled Opinio et consilium super processu et condemnatione Johanne, dicte Puelle and other miscellaneous writings. He wrote in French, Advis de Monseigneur de Lysieux au roi (Paris, 1677).