William Gilson Farlow (December 17, 1844 – June 3, 1919) was an American botanist.

Farlow was born on December 17, 1844, in Boston, and educated at Harvard (A.B., 1866; M.D., 1870), where, after several years of European study, he became adjunct professor of botany in 1874 and professor of cryptogamic botany in 1879.

[1] Farlow corresponded with Caroline Bingham and Jacob Georg Agardh collaborating in the identification and classification of species of algae previously unknown to science.

[8] Between 1922 and 1946 the Farlow Herbarium distributed the exsiccata Reliquiae Farlowianae.

Cryptogams distributed by the Farlow Herbarium of Harvard University, the first part edited by Roland Thaxter (no.