Elizabeth Ann Theresa Lynn was an American actress. She played Thelma Lou, Deputy Barney Fife's girlfriend, on The Andy Griffith Show. During the 1940s and 1950s, she appeared in many films, including Sitting Pretty (1948), June Bride (1948), the original Cheaper by the Dozen (1950), and Meet Me in Las Vegas (1956). She also played a major role in an episode of the television series Little House on the Prairie.

Thelma Lou, or Thel by boyfriend Barney Fife, is a character on the American television sitcom The Andy Griffith Show (1960-1968). The character appeared in 26 episodes, starting with the first-season episode, "Cyrano Andy". Thelma Lou was portrayed by Betty Lynn.