Michael Francis Fay (born 1960) is a British geneticist and botanist currently serving as Senior Research Leader, Conservation Genetics, at the Royal Botanic Gardens, Kew.
After studying at University College of Wales, Aberystwyth and the Welsh Plant Breeding Station, Fay was awarded a PhD in 1989 for his thesis on genetic resources in Trifolium (clover).
In 2000, he received the Bicentenary Medal of the Linnean Society, and has served on its governing council for several terms since 2003.
He is currently Co-Chair of the Orchid Specialist Group of the Species Survival Commission of IUCN.
Among many other publications, he is an author of all iterations to date of the Angiosperm Phylogeny Group, and in 2017 he co-authored an encyclopedia on vascular plants entitled Plants of the World with Maarten Christenhusz and Mark Wayne Chase.