Floyd Glenn Lounsbury (April 25, 1914 – May 14, 1998) was an American linguist, anthropologist and Mayanist scholar and epigrapher, best known for his work on linguistic and cultural systems of a variety of North and South American languages. Equally important were his contributions to understanding the hieroglyphs, culture and history of the Maya civilization of pre-Columbian Mesoamerica.
 Lounsbury was born in Stevens Point, Wisconsin to John Glenn Lounsbury and Anna Louise Jorgensen. He was one of three children - he had a brother, Gordon, and a sister, Elva.
 He graduated from the University of Wisconsin in 1941, majoring in Mathematics. During the period, Morris Swadesh was on the faculty, lecturing on American Indian linguistics. Lounsbury audited his courses, and when Swadesh received grants from the Works Progress Administration for a study of Oneida language and folk lore, he appointed Lounsbury as his assistant. When Swadesh left Wisconsin for Mexico City, Lounsbury took over as the director of the project. He created an orthography for the language, and taught it to students who gathered a variety of texts from Oneida language speakers. After the project, Lounsbury began work in 1940 on the phonology of the language for his master's degree at the university.
 When World War II broke out, he enrolled as a meteorologist in the XXII Weather Squadron, US Army Air Corps. Stationed in Brazil, he learned Portuguese there. He received his master's degree in 1946. Awarded a fellowship by the Rockefeller Foundation, he worked on Oneida verb morphology in the department of anthropology at Yale. He received his Ph.D. in 1949 (his chair was Bernard Bloch), and his dissertation formed the basis of a publication in 1953 that established a framework and terminology followed ever since in the analysis of Iroquoian languages. He joined the department in 1949, and taught there until his retirement in 1979.
 He traced the historical relationship between various Iroquoian languages, and as part of his work for the New York Vermont Interstate Commission on the Lake Champlain Basin, wrote an authoritative study of Iroquois place names in the Champlain Valley. He initiated the application of linguistic methods to the formal analysis of kinship terminology and social organization. He also recorded the Oneida Creation myth in 1971 in Ontario, which was to result in a book, published posthumously by his student Bryan Gick, that included the creation myth and references to versions translated earlier, and linguistic analysis of various aspects of Iroquoian stories.
 His linguistics work also had a bearing on his anthropological studies - he used his knowledge of semantic fields to relate kin type to phones in the field of phonetics.(Lounsbury 1956)
Lounsbury was an early proponent of Yuri Knorozov's phonetic theory on the Maya hieroglyphs, that they were syllables rather than ideograms. He contributed to the methodology that ultimately led to the deciphering of the hieroglyphs. He was part of the trio, Linda Schele and Peter Mathews being the others, that one afternoon in 1973, worked out a 200-year timeline of the Palenque royal family, presenting it that evening at the First Palenque Round Table.
 During this period, Lounsbury studied the Venus almanac in the Dresden codex and concluded that the original Goodman correlation fits the evidence in the codex better than the standard Goodman-Martinez-Thompson correlation. A correlation constant is the number of days between the start of the Julian Period (January 1, 4713 BCE) and the era date of the Long Count of 13.0.0.0.0 4 Ajaw 8 Kumk'u. It is used to convert between the Long Count and western calendars. The Goodman correlation constant is 584,285, two days more than the standard GMT correlation of 584,283.
 He lived in East Haven, and died of congestive heart failure at Connecticut Hospice.
 He married Masako Yokoyama and they had a daughter, the novelist and film-maker Ruth Ozeki.