Thomas Hakon Grönwall or Thomas Hakon Gronwall (January 16, 1877, Dylta bruk, Sweden - May 9, 1932, New York, USA) was a Swedish mathematician. He studied at the University College of Stockholm and Uppsala University and completed his Ph.D. at Uppsala in 1898. Grönwall worked for about a year as a civil engineer in Germany before he immigrated to the United States in 1904. He later taught at Princeton University and Columbia University.