Robert E. Longacre (August 13, 1922–April 20, 2014) was an American linguist and missionary who worked on the Triqui language and a text-based theory and method of discourse analysis. He is well known for his seminal studies of discourse structure (text linguistics), but he also made significant contributions in other linguistic areas, especially the historical linguistics of Mixtec, Trique, and other related languages. His PhD was at the University of Pennsylvania under Zellig Harris and Henry Hoenigswald. His 1955 dissertation on Proto-Mixtecan was the first extensive linguistic reconstruction in Mesoamerican languages. This was one of several SIL studies which helped to establish the Oto-Manguean language family as being comparable in time depth to Proto-Indo-European. His research on T