Parasitic nutrition is a mode of nutrition where organism (known as a parasite) lives on the body surface or inside the body of another type of organism and obtains nutrition directly from the body of the other organism (known as a host). Since these parasites derive their nourishment from their hosts, this symbiotic interaction is often described as harmful (to the subject of host).

Most parasites are so tiny in size and some are even invisible to the naked eye of a human. Many parasites have complex life cycles involving multiple hosts.