Timothy Field Allen (April 24, 1837 – December 5, 1902) was an American physician and botanist.

Becoming associated professionally with Dr. Carroll Dunham, he early adopted homeopathy, and soon rose to a prominent position among homeopathic practitioners.

Early in his career he became a botanical enthusiast, and maintained his interest in this branch of scientific study in spite of his arduous professional work.

He was the first to occupy the office of vice-president in the Club, and was re-elected annually until his death nearly thirty years later.

This difficult group of algae has attracted but few botanists, and for many years he was almost the only American student of these plants.

His "Contributions to Japanese Characeae," first printed in instalments in the Bulletin of the Torrey Botanical Club from 1894 to 1898, also appeared separately in pamphlet form.

[2][3][4] By correspondence, by exchange, by purchase, and by paying the expenses of collectors in North America, South America, and Japan, Allen brought together one of the finest accumulations of specimens and books relating to the Characeae in existence; all these he presented to the New York Botanical Garden the year before his death, when failing health made it impossible for him to study them further.