What was the name of Barney Fife's girlfriend on the show?

Barney Fife’s girlfriend on The Andy Griffith Show was Thelma Lou.

Played by Betty Lynn, Thelma Lou was Barney’s principal romantic interest in Mayberry. She first appeared in the season-one episode “Cyrano Andy,” and her relationship with Barney became a recurring source of gentle comedy. Barney’s insecurity, jealousy, and exaggerated self-importance often complicated their otherwise affectionate courtship.

Thelma Lou appeared in 26 episodes between 1961 and 1966. Her character was dropped after Don Knotts left the regular cast, as Barney moved away from Mayberry to join the Raleigh police force. In the episode “The Return of Barney Fife,” Barney discovers that Thelma Lou has married Gerald Whitfield, although that marriage later ends.

Viewers sometimes confuse Thelma Lou with Juanita, a waitress Barney mentions and dates, or with Helen Crump, Andy Taylor’s girlfriend. Thelma Lou is the character most consistently identified as Barney’s girlfriend. In the 1986 reunion film Return to Mayberry, Barney and Thelma Lou finally marry.