Ciboria betulae is a small discomycete fungus in the family Sclerotiniaceae, associated with birch (Betula) trees across temperate Europe and northern Asia. The species fruits on fallen birch catkins, seeds, or occasionally on decaying birch wood in moist woodland habitats and riparian zones. Its fruiting bodies are typical of the genus: small, stalked cup fungi with a pale to medium brown, concave disc surface. Ciboria betulae is saprotrophic, breaking down plant debris and contributing to nutrient cycling in birch woodland ecosystems. The species name clearly references its host association with Betula. It is classified as Least Concern, reflecting a distribution that is wide, though perhaps locally patchy, across birch-dominated forests and woodland edges. Birch catkins provide a specific substrate window in late spring and early summer after they fall, meaning the fruiting season of this species is typically brief and easily missed. Microscopic features including ascospore dimensions and shape, paraphysis morphology, and excipular tissue help differentiate Ciboria betulae from closely related species on other substrates. The genus Ciboria encompasses multiple species each associated with particular plant substrates, representing a degree of substrate specialization unusual among saprotrophic cup fungi. Records are scattered but consistent across the temperate birch belt of Eurasia.