The Monstrous Inmate is a minor antagonist in the 2014 Marvel Cinematic Universe superhero film Guardians of the Galaxy. He is an unnamed alien criminal held in the space prison Kyln.
He was portrayed by Nathan Fillion, who also played Johnny Worthington III in the Monsters, Inc. franchise, Karja in Guardians of the Galaxy Vol. 3, and Headpool in Deadpool & Wolverine.