Henricus (Harrie) Johannes Maria Sipman (born 1945) is a retired Dutch lichenologist who specialised in tropical and subtropical lichens and authored or co-authored over 250 scientific publications.
During this time, some of his research publications dealt with taxa from the lichen genera Cladonia and Stereocaulon, and on the Musci Anisothecium staphylinum, Campylopus and Ephemerum.
He earned his PhD in 1983 after defending a thesis on the family Megalosporaceae, later published as a monograph in the Bibliotheca Lichenologica series.
[5] Frequent collaborators include André Aptroot, Teuvo Ahti, Paul Diederich, Mark Seaward, Emmanuël Sérusiaux and Richard Harris.
Many of his publications deal with lichen floras of tropical and subtropical countries such as Colombia, Costa Rica, Guiana and New Guinea.