Rex Bertram Filson (born 1930) is an Australian lichenologist who made major contributions to knowledge of lichens in Australia and Antarctica.

Employment with the Victorian Department of Crown Lands and Survey followed (1964–1988), first as a seed-collector and finally as senior botanist.

[1] In 1970, Filson was awarded a Churchill Fellowship to compare northern hemisphere with Australian lichens.

[2] The National Herbarium of Victoria holds the majority of Filson's collections, over 15,000 specimens, with duplicates distributed around Australian Herbaria including AD, BRI, CANB, HO, NSW and PERTH, with several in overseas herbaria such s MSK, GZU, F and UPS.

[4] Filson Nunatak in Antarctica is named in his honour,[5] as is the lichen genus Filsoniana.