The therian subclass of mammals are those which bear live young, including both placentals and marsupials. Almost all currently extant mammals are therians. The only exceptions are the platypus and the echidnas (spiny anteater), both of which are monotremes.

Therian is also another term for a therianthrope, used predominantly in the context of the modern subculture by that name rather than the mythological/folkloric motif.