Nellie Adalesa Brown (1876–1956) was an American botanist and government researcher.

While working with Charles Orrin Townsend[1] and Agnes J. Quirk[2] as assistants for Erwin Frink Smith, Brown and her colleagues described Agrobacterium tumefaciens, the organism responsible for crown gall in 1907.

[6] While doing post-graduate work at University of California, Brown became a member of the Torrey Botanical Club.

From 1915 to 1918 she began studying bacterial diseases in lettuce, and eventually published research under her own name.

[8] In the mid-twenties, Brown was promoted to associate pathologist, a position she held until her retirement in 1941.