Brown Jenkin is a rat-like creature with a human-like face who is a familiar to Keziah Mason and a secondary antagonist of H.P. Lovecraft's short story "Dreams in the Witch House". He is also part of the same race of strange rats with human faces called the Rat Things.
Brown Jenkin, Mason's familiar, is "a small white-fanged furry thing", "no larger than a good-sized rat", which for years haunts the witch house and the town of Arkham in general, "nuzzl[ing] people curiously in the black hours before dawn". The creature is described: Witnesses said it had long hair and the shape of a rat, but that its sharp-toothed, bearded face was evilly human while its paws were like tiny human hands. It took messages betwixt old Keziah and the devil, and was nursed on the witch's blood, which it sucked like a vampire. Its voice was a kind of loathsome titter, and it could speak all languages.