Gaspar Lax (1487, Sariñena – 23 February 1560, Saragossa) was a Spanish mathematician, logician, and philosopher who spent much of his career in Paris.
Lax studied the Seven Liberal Arts and theology at the University of Saragossa, where he acquired a master's degree. He taught in 1507–1508 at the Collège de Calvi in Paris and then at the Collège de Montaigu, where he was a student of John Mair (or Major) and simultaneously was a teacher himself. From 1517 Lax was again at the Collège de Calvi. In Paris he was known as the "Prince of Sophists". He taught in Paris until 1523 and then returned to Spain because in that year all foreigners were requested to leave the Parisian universities. Starting in 1525 he taught mathematics and philosophy at the University of Saragossa and remained there until his death. In addition to his teaching, Lax was vice-chancellor and rector of the University of Saragossa.