William Nylander

William (Wilhem) Nylander (3 January 1822 – 29 March 1899) was a Finnish botanist and entomologist. Nylander was born in Oulu, and taught at the University of Helsinki for a number of years before later moving to Paris, where he lived until his death in 1899.

Nylander pioneered the technique of determining the taxonomy of lichens by the use of chemical reagents, such as tinctures of iodine and hypochlorite, still used by lichenologists to this day.

Nylander was also the first to realise the effect of atmospheric pollution on the growth of lichens, an important discovery that paved the way for the use of lichens to detect pollution and determine the cleanness of air.