Ugly Naked Guy was a character in the American television show, Friends. The character was never shown on screen until his final appearance when he was shown with his back facing the camera. His actual name is not known. He received his nickname for being fat and ugly, as well as being naked while at home. He wasn't always Ugly Naked Guy, though. In an episode that was supposed to take place before the series started, the gang referred to him as Cute Naked Guy, but commented that he had been putting on a lot of weight recently.

Ugly Naked Guy lived in an apartment directly opposite Rachel and Monica's apartment. Anyone in the girls' apartment could look directly into Ugly Naked Guy's apartment. Throughout the early years, the gang would look into Ugly Naked Guy's apartment and comment on his going ons, such as him getting a ThighMaster or squashing his cat by accidentally sitting on it.

In one episode it was announced that Ugly Naked Guy was moving out and subletting the apartment. This sparked a frenzy of bids, along with bribes. Ross Geller ended up acquiring the apartment by dancing naked with him, to the shock and amusement of the rest of the gang looking from Rachel and Monica's apartment.

Ugly Naked Guy was never heard of again, and did not appear in the last episode, against the norm of the episode.