Thielavia is a genus of fungi in the family Chaetomiaceae. Circumscribed by German botanist Friedrich Wilhelm Zopf in 1876, Thielavia is a teleomorph of . Collectively, the genus is widely distributed, and according to a 2008 estimate, contained 31 species. and can cause infections in humans. The genus name of Thielavia is in honour of Friedrich Joachim Sigismund von Thielau (1796–1870), who was a German forester and landowner in Breslau.