This article is for the herb pennyroyal. See Pennyroyal Tea for the Nirvana song.

The herb Pennyroyal (Mentha pulegium, Lamiaceae), is a member of the mint genus; an essential oil extracted from it is used in aromatherapy. Pennyroyal has a traditional folk medicine use in inducing abortions and is an abortifacient.

The oil is also used as a flea repellant for pets. This latter usage is the origin of the plant's Latin species name, the flea being Pulex irritans. However the distantly related American Pennyroyal or Hedeoma pulegioides is the source of much of what is called pennyroyal oil.

The term Pennyroyal (or Pennyrile, from a dialectical pronunciation) is also used to describe a geographic province of western Kentucky where the above-described herb grew in profusion sufficient to lend its name to the whole area.