Karl Brendel is the pseudonym of Karl Genzel (21 March 1871 – 21 August 1925), a schizophrenic outsider artist and one of the "schizophrenic masters" profiled by Hans Prinzhorn in his field-defining work Artistry of the Mentally Ill (1923, in German; English edition 1972).
He was the only sculptor profiled in Prinzhorn's work, and the work also includes more illustrations of his work (twenty-four sculptures and eight drawings) than that of any other profiled artist.