The GILA monster is a species of venomous lizard native to the southwestern United States and northwestern Mexico. It is the only venomous lizard native to the United States, and one of only two known species of venomous lizards in North America. The GILA monster is a large lizard, growing up to 24 inches in length, and is characterized by its bright orange or yellow coloration and black markings. It is a slow-moving creature, but it is capable of delivering a painful bite if provoked. As such, it is considered to be a poisonous lizard.