Isidore Dyen (16 August 1913 in Philadelphia – 14 December 2008 in Newton, Massachusetts) was an American linguist, Professor Emeritus of Malayo-Polynesian and Comparative Linguistics at Yale University. He was one of the foremost scholars in the field of Austronesian linguistics, publishing extensively on the reconstruction of Proto-Austronesian phonology and on subgrouping within the language family, the latter principally by means of lexicostatistics.