Geosmin is an organic compound with a distinct earthy flavor and aroma produced by a type of Actinobacteria, and is responsible for the earthy taste of beets and a contributor to the strong scent (petrichor) that occurs in the air when rain falls after a dry spell of weather or when soil is disturbed. In chemical terms, it is a bicyclic alcohol with formula , a derivative of decalin. Its name is derived from the Greek γεω- "earth" and ὀσμή "smell".