Diphallia is a rare condition in which a male is born with two penises. It is believed to occur during fetal gestation when stress, chemical interference, or genetic abnormality causes a split and two penises form independently. In many cases, there are other genital and urinary abnormalities, such as duplicate scrotums, bladders, and kidneys.
Diphallia is also known as penile duplication (PD), diphallic terata, diphallasparatu, or diphallus. Colloquially, it is often called double dick.