The Frumious Bandersnatch is one of the antagonists in the poem "The Hunting of the Snark" written by the late Lewis Carroll (with the other being the Boojum Snark. It is a savage creature that lives on the same island as the Boojum Snark and the JubJub bird.
The Frumious Bandersnatch is first mentioned in the poem "Jabberwocky", where the protagonist is told to beware the Jabberwock and the JubJub bird, and to "shun the Frumious Bandersnatch". It next appears in "The Hunting Of The Snark: Fit the seventh: The Banker's Fate", in which the Banker, looking for the Snark, is attacked and grabbed by a Bandersnatch. He tries to bribe it with a discount and a cheque for seven pounds ten drawn "to bearer", but it begins to bite him until he faints. The others hear the screaming and come running, chasing it away, however when the Bellman brings him round he discovers the Bandersnatch sent him mad.