A penis (plural penises or penes /-/) is the main sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs are found in many animals, both vertebrate and invertebrate, but males do not always have a penis in every species, and in those species in which the male does have a so-called penis, the penises in those species are not homologous.
- Janet Leonard; Alex Cordoba-Aguilar R (18 June 2010). The Evolution of Primary Sexual Characters in Animals. Oxford University Press. ISBN 978-0-19-971703-3. Archived from the original on 11 October 2013. Retrieved 20 July 2013.