Joanne Finn is the wife of dolphin Billy Finn. After Billy takes Peter Griffin up on his offer of a favor and leaves his wife to live on dry land in "Be Careful What You Fish For", she dumps him. But when Billy proves to be an unwelcome house guest, Peter plots to get them back together so Billy will leave. Joanne at first rejects Peter's attempt by having Glenn Quagmire dress as Aquaman and Joe Swanson as Neptune, but when Billy opens up and apologizes to her she takes him back.

Joanne is voiced by Lucy Davis.