Thomas Messinger Drown (March 19, 1842 – November 17, 1904) was the fourth University President of Lehigh University in Bethlehem, Pennsylvania, United States. He was also an analytical chemist and metallurgist.
He was born in Philadelphia, Pennsylvania in 1842. He graduated from Central High School in Philadelphia in 1859, and then went on to study medicine at the University of Pennsylvania and graduated in 1862. He went abroad to Germany to study chemistry in Freiberg, Saxony, and mining at the University of Heidelberg. From 1869 to 1870 he was an instructor of metallurgy at Harvard University. In 1870, he started a consulting business in Philadelphia. In 1872, he hired a former student, John Townsend Baker, as an assistant. From 1874 to 1881, he was professor of Analytical Chemistry at Lafayette College. Baker followed him to Lafayette and later would found the J. T. Baker Chemical Co., which merged with Mallinckrodt and was absorbed and spun off of Tyco International as a component company of Covidien.
His professional career was interrupted in 1881, when, after the death of his father, he devoted himself to family matters. He restarted his professional work in 1885 by accepting a professorship at the Massachusetts Institute of Technology.