Polycephaly is the condition of having more than one head. The term is derived from the Greek stems poly (Greek: "????") meaning "many" and kephale (Greek: "??????") meaning "head". A polycephalic organism may be thought of as one being with a supernumerary body part, or as two or more beings with a shared body.

Two-headed animals (called bicephalic or dicephalic) and three-headed