Liir is Elphaba's son in Gregory Maguire's apocryphal prequels to The Wonderful Wizard of Oz. He is friends with Dorothy Gale, Toto, the Scarecrow, the Tin Woodman, and the Cowardly Lion. (Wicked: The Life and Times of the Wicked Witch of the West and Son of a Witch)
Liir is a boy who leaves the mauntery with Elphaba for the Vinkus. It is at first only strongly implied that Liir is the son of Elphaba and Fiyero, since Elphaba develops motherly feelings toward Liir. She does indeed admit that there is a year of her life she does not remember, during which she could have given birth to Liir. Extremely chubby, Liir plays with his supposed half-siblings while he and Elphaba stay with Fiyero's widow. At the end of Wicked it is stated that he intends to find a way of rescuing his half-sister Nor from her slavery.
Liir is also the protagonist of Maguire's sequel to Wicked, Son of a Witch. In this book, Liir unknowingly impregnates a Quadling girl named Candle, which results in the birth of a green baby. This finally proves that Liir is indeed the son of Elphaba and Fiyero.
Gregory Maguire has described Liir as "Elphaba's bastard son" in interviews.