Gunnar Seidenfaden was a Danish diplomat and botanist. He was Danish ambassador in Thailand 1955–1959, and in the U.S.S.R. 1959–1961. He was an expert on Southeast Asia Orchidaceae. He published several multi-volume works on orchids, e.g. The Orchids of Thailand – A Preliminary List and Orchid Genera in Thailand vol. I- XIV. These works are strictly taxonomic and floristic, but decorated with Seidenfaden's own drawings of flower parts as seen under the dissection microscope. His collection of more than 10,000 specimens was donated to the University of Copenhagen, together with original drawings by Katja Anker and others.
In June 2016, it was decided that the collection of orchid samples, which was held in the Danish capital botanical garden Botanisk Have, part of the natural history museum Statens Naturhistoriske Museum, would be returned to Thailand. The reason given was that many of the specimens have become quite rare and the aim is to multiply as many species as possible in sufficient scale so that young plants can be returned to their country of origin.