How many fungal species are there?

We know only a small part of fungal diversity. A 2021 review said that nearly 150,000 fungal species had been described by then. The estimated total is much larger: a 2017 study put it at 2.2–3.8 million species. That range is an estimate, not a complete census, so the exact number remains unknown. A “described species” is one formally named and documented by scientists.