Karl Bartholomaeus[1] Heller (20 November 1824 – 14 December 1880) was an Austrian botanist and naturalist who explored Mexico in 1845–48 and published his memoir.
[2] In the latter year Johann Jakob Heckel published the livebearing freshwater Green swordtail (Xiphophorus helleri), since the early 20th century a common aquarium fish, from specimens Heller deposited in Vienna.
Born in Moravia, Heller was a professor at the Theresianum in Vienna.
Among Heller's later works is his defense of Darwinism, Darwin und der Darwinismus, 1869.