Cyathus striatus, commonly known as the fluted bird's nest, is a common saprobic bird's nest fungus.

This fungus resembles a miniature bird's nest with numerous tiny "eggs"; the eggs, or peridioles, are actually lens-shaped bodies that contain spores. The color and size of this species can vary somewhat, but they are typically less than a centimeter wide and tall, and grey or brown in color. The common name splash cups alludes to the method of spore dispersal: the sides of the cup are angled such that falling drops of water can dislodge the peridioles and eject them from the cup. C. striatus can be distinguished from most other bird's nest fungi by its hairy exterior and grooved (striated) inner walls.

Although most frequently found growing on dead wood in open forests, it also grows on wood chip mulch in urban areas. The fruiting bodies are encountered from summer until early winter. with a widespread distribution throughout temperate regions of the world.