Hybrid beasts are creatures composed of parts from different animals, including humans, appearing in the folklore of a variety of cultures as legendary creatures.

Remains similar to those of mythological hybrids have been found in burial sites discovered by archaeologists. Known combinations include horse-cows, sheep-cows, and a six-legged sheep. The skeletons were formed by ancient peoples who joined together body parts from animal carcasses of different species. The practice is believed to have been done as an offering to their gods.

These forms' motifs appear across cultures in many mythologies around the world.

Such hybrids can be classified as partly human hybrids (such as mermaids or centaurs) or non-human hybrids combining two or more non-human animal species (such as the griffin or the chimera). Hybrids often originate as zoomorphic deities who, over time, are given an anthropomorphic aspect.

Partly human hybrids appear in petroglyphs or cave paintings from the Upper Paleolithic, in shamanistic or totemistic contexts. Ethnologist Ivar Lissner theorized that cave paintings of beings combining human and animal features were not physical representations of mythical hybrids, but were instead attempts to depict shamans in the process of acquiring the mental and spiritual attributes of various beasts or power animals. Religious historian Mircea Eliade has observed that beliefs regarding animal identity and transformation into animals are widespread.

Examples of humans with animal heads (theriocephaly) in the ancient Egyptian pantheon include jackal-headed Anubis, cobra-headed Amunet, lion-headed Sekhmet, and falcon-headed Horus. Most of these deities also have a purely zoomorphic and a purely anthropomorphic aspect, with the hybrid representation seeking to capture aspects of both of which at once. Similarly, the Gaulish Artio sculpture found in Bern, Switzerland shows a juxtaposition of a bear and a woman figure, interpreted as representations of the theriomorphic and the anthropomorphic aspect of the same goddess.

Non-human hybrids also appear in ancient Egyptian iconography, as in Ammit (combining the crocodile, lion, and hippopotamus).

Mythological hybrids became very popular in Luwian and Assyrian art of the Late Bronze Age to Early Iron Age. The angel (human with birds' wings, see winged genie) the mermaid (part human part fish, see Enki, Atargatis, and Apkallu) and the shedu all trace their origins to Assyro-Babylonian art. In Mesopotamian mythology the urmahlullu, or lion-man, served as a guardian spirit, especially of bathrooms.