Betty Lynn, who portrayed Thelma Lou, the patient girlfriend of Barney Fife, the neurotic deputy sheriff of Mayberry in the 1960s sitcom “The Andy Griffith Show,” died on Saturday in Mount Airy, N.C. She was 95.

The death was announced by the Andy Griffith Museum in Mount Airy, Mr. Griffith’s hometown and the inspiration for Mayberry.

Ms. Lynn joined the cast of the show in 1961, late in the first season, for an episode in which Sheriff Andy Taylor (Mr. Griffith) plays matchmaker between Barney and Thelma Lou.

Thelma Lou’s occupation through 26 episodes remained a mystery, as did her surname. Although Barney (Don Knotts) had an occasional telephone flirtation with Juanita, a diner waitress who was never seen, it was clear that Thelma Lou was Barney’s steady girl. But in a 1966 episode, after Mr. Knotts’s departure as a series regular, Barney returned for a high school reunion to learn that Thelma Lou had gotten married.

When much of the cast reunited in 1986 for “Return To Mayberry,” a two-hour television movie, Thelma Lou had gotten divorced. She and Barney married in the film.

In 2007, Ms. Lynn moved from West Hollywood to a retirement community in Mount Airy, which in addition to the Griffith museum, has built recreations of familiar Mayberry haunts like Floyd’s barber shop. Ms. Lynn became a nostalgic lure to tourists who stood in line once a month for her autograph, to give her a kiss or chat about the series.

“I think God’s blessed me,” she told The Associated Press in 2015. “He brought me to a sweet town, wonderful people, and just said, ‘Now, that’s for you, Betty.’”

Elizabeth Ann Theresa Lynn was born on Aug. 29, 1926, in Kansas City, Mo. Her mother, Elizabeth, was a singer, organist and church choir director who raised Betty with her parents. By 14, Betty was singing in local supper clubs and at 18 she began performing in U.S.O. shows. After the war, she had small roles in the Broadway musicals “Park Avenue” and “Oklahoma!”

She appeared in films like “Sitting Pretty” and “June Bride” in 1948 and “Cheaper By the Dozen” in 1950. On television, she acted in anthology series, westerns and sitcoms, including “Family Affair and “My Three Sons.” In 1986, she played Mr. Griffith’s secretary on four episodes of his dramatic series, “Matlock,” in which he played a lawyer.

Ms. Lynn never married and did not have any immediate survivors. And among regular cast members of “The Andy Griffith Show,” only Ron Howard, who played Opie, Sheriff Taylor’s son, is still alive.

She said that she could have stayed with the series, which ended in 1968, had she accepted the producers’ offer to make her the owner of a hairdressing salon. But Mr. Knotts was gone, having moved on to a film career.

Without Barney, she told The A.P. in 2007, “I didn’t think Thelma Lou made much sense.”