Otto Christian Leonor Gelert (9 November 1862 in Nybøl on Sundeved peninsula – 20 March 1899 in Copenhagen) was a Danish pharmacist and botanist, who specialized in plant floristics and systematics.
In 1883 he received his degree in pharmacy and subsequently worked as a druggist in the communities of Ribe and Horsens.
In 1885 he started to co-edit the exsiccata series Rubi exsiccati Daniae et Slesvigiae together with Peter Kristian Nicolaj Friderichsen.
[1] From 1894 he worked as chemist at a sugar refinery in Tangermünde, Germany.
[2] During the latter part of his career he worked at the botanical museum in Copenhagen.