Lucien Marcus Underwood (October 26, 1853 – November 16, 1907) was an American botanist and mycologist of the 19th and early 20th centuries.

[2][5] After a year's teaching at Hedding College, in 1880 he was appointed professor of geology and botany in Illinois Wesleyan University.

[4] In 1890, he accepted the Morgan Fellowship at Harvard University to study the Sullivant and Taylor collection of hepatics.

[8][9][10][11] Underwood's papers are maintained at the LuEsther T. Mertz Library of the New York Botanical Garden.

[6] After losing large amounts of money on Wall Street in the Panic of 1907, Underwood attempted to murder his wife and daughter before committing suicide at the family's home in Redding, Connecticut.