Biology appears in fiction, especially but not only in science fiction, both in the shape of real aspects of the science, used as themes or plot devices, and in the form of fictional elements, whether fictional extensions or applications of biological theory, or through the invention of fictional organisms. Major aspects of biology found in fiction include evolution, disease, genetics, physiology, parasitism and symbiosis (mutualism), ethology, and ecology.

Parasites appear frequently in biology-inspired fiction from ancient times onwards, with a flowering in the nineteenth century. These include intentionally disgusting alien monsters in science fiction films, often with analogues in nature. Authors and scriptwriters have, to some extent, exploited parasite biology: lifestyles including parasitoid, behaviour-altering parasite, brood parasite, parasitic castrator, and many forms of vampire are found in books and films. Some fictional parasites, like Count Dracula and Alien's Xenomorphs, have become well known in their own right.