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.
In the poem "Bandersnatchy" by Anna Matlack Richards, a man who knows the man who killed the Jabberwock decides to hunt the Bandersnatch in order to eclipse him, as he constantly goes on about how he killed it. He arms himself with a vorpal sword and a winxy pistol, and goes out to hunt it. In the forest, he notices two of the trees are in fact the legs of some gigantic creature, which he realises is the Bandersnatch. It tries to flee, but he cuts it in two, and brings its tail back as proof that he killed the Bandersnatch. The poem ends with the hero noting that since then, he hasn't heard about the Jabberwock as much.