"Sredni Vashtar" is a short story written by Saki (Hector Hugh Munro) between 1900 and 1911 and initially published in his book The Chronicles of Clovis. It has been adapted for opera, film, radio and television.

The story concerns an unhealthy ten-year-old boy named Conradin, who lives with his strict cousin and guardian, Mrs. De Ropp. Conradin rebels against her and invents a new religion for himself, which centres on idolising a polecat-ferret he calls Sredni Vashtar; he imagines Sredni Vashtar to be a vengeful, merciless god. Conradin keeps the ferret hidden in a cage in the garden shed, and worships the idol in secret. The story comes to a climax when his cousin sets out to discover his god.