Roussoëlla is a genus of fungi in the family Roussoellaceae.

[1] The genus is characterized by two-celled ascospores, unitunicate asci with a small spherical apical ring that stains slightly blue with Melzer's reagent, and stromata with several perithecia.

[2] The genus was circumscribed by Italian mycologist Pier Andrea Saccardo in 1888, with Roussoella nitidula assigned as the type species.

[3] The generic name honours Marietta Hannon Rousseau,[4] (1850–1926), who was a Belgian mycologist and taxonomist.

[5] Roussoellaceae was introduced by Liu et al. (2014) and contains three genera; Neoroussoella, Roussoella and Roussoellopsis.