Otto Sendtner (27 June 1813 – 21 April 1859) was a German botanist and phytogeographer born in Munich.
He received his education at the University of Munich, where he was a student of Karl Friedrich Schimper (1803–1867).
Afterwards he served as a private secretary to a Silesian nobleman, and during his spare time performed studies of cryptogramic flora of the Sudetenland.
In 1854 he became an associate professor, and in 1857 was appointed to the second chair of botany, as well as first curator of the herbarium at the University of Munich.
Sendtner was a pioneer in the field of phytogeography, and in his research conducted important analyses involving the vertical distribution patterns of different types of vegetation.