This article is about a biological term. See hybrid (disambiguation) for other meanings.

In biology, hybrid has two meanings. The first meaning is either the offspring of two different species, or of two different genera. The second meaning of "hybrid" is crosses between populations or cultivars ("cultivated varieties") of a single species. This second meaning is often used in plant breeding. Hybrids between species of the same genus are sometimes known as interspecific hybrids or crosses. Hybrids between different genera are sometimes known as intergeneric hybrids. Animal hybrids are commonly known as crossbreeds or crossbreds.

Ernst Mayr wrote of Gregor Mendel, "He was uncertain about the nature of the kinds of peas he crossed, and, like most plant breeders, he called heterozygotes "hybrids." When he tried to confirm the laws he had found by using "other hybrids" that were actually real species hybrids, he failed. The use of the same term "hybrid" for two entirely different biological phenomena thwarted his later efforts." (This is Biology, 1997, p58f).

Some dog hybrids (used in sense two, above), are becoming increasingly popular and are being bred selectively.

Plant hybrids, especially, may or may not be stronger than either parent variety, a phenomenon which when present is known as hybrid vigour. To create specialised plants is called cross-fertilisation. In animals, hybrids often manifest reduced fertility or, like the mule are sterile.

Some interspecies hybrids are:

• Mule, a cross of female horse and a male donkey.
• Hinny, a cross between a female donkey and a male horse.
  

  

  A "Zeedonk", a zebra/donkey hybrid
• Zeedonk, a zebra/donkey cross.
• Zorse or zebroid, a zebra/horse cross
• Dzo or zo: a cross between a domestic cow/bull and a yak.
• Beefalo, a cross of an American Bison and a domestic cow. This is a fertile breed, although the two species are in different genera (Bison and Bos, respectively).
• Hybrids between sheep and goat.
• Wolfdog, the cross between a domestic dog and a Wolf. Crosses also occur between coyote, wolves, dingos, and domestic dogs. Many of these produce fertile animals ("dog" & "wolf" are now usually considered the same species, so this may be considered a non-hybrid).
• Hybrids between spotted owls and barred owls
• Liger (or Tigon, depending on the parents' genders), a cross between a Lion and a Tiger. Various other wild cat crosses are known involving the Lynx, Bobcat, Leopard, Serval, etc.
• Cama, a cross between a Camel and a Llama, also an intergeneric hybrid.
• Wolphin, a fertile but very rare cross between a whale and a dolphin.
• A fertile cross between an albino King Snake and an albino Corn Snake.
• At Chester Zoo in England, a cross between African elephant (male) and Indian elephant (female). The calf was named Motty. It died of gut infection after a few days.
• Cagebird breeders sometimes make hybrids between species of finch, such as goldfinch x canary.
• Leyland Cypress, a hybrid between Monterey Cypress and Nootka Cypress.
• London Plane, a hybrid between Oriental Plane and American Plane (American Sycamore).
• Tangelo, a hybrid of a mandarin orange and a pummelo or a grapefruit which may have been developed in Asia about 3,500 years ago.

Hybrids should not be confused with chimaeras.

Mythological and legendary hybrids

In ancient and modern local folktales, there exist hybrids resulting from the union between a human parent and an animal or a non-human sentient being. Some of these hybrids are crosses with humans and: brownies, nymphs, gods, Moo-Moo (Solomon Island Giant), chimpanzees (Humanzee), aliens, bats (Batboy), snakes/lizards (Naga, Syrictae), dropa, giants, cat people, mermaids, fairies, watchers, demons, dryads, spirits, incubus, succubus, pech, triton, larvae, martes, and others. One example is the Minotaur.