Gladys Swarthout was an American mezzo-soprano opera singer. She was born in Deepwater, Missouri.
While studying at the Bush Conservatory of Music in Chicago, a group of friends arranged an audition for her with the Chicago Civic Opera Company. Much to her surprise, she ended up with a contract, though at the time she didn't know a single operatic role. By her debut a few months later, she had memorized 23 parts and participated in over half of the season's operas. She sang for the Ravinia Opera Company of Chicago for three seasons. In 1929, she made her debut with the New York Metropolitan Opera Company, where she was a participant for several decades.
She regularly worked eight hours a day with vocal coaches, and would spend an hour or more singing duets with her husband. She also advocated inflating balloons and blowing bubbles to strengthen the chest.
She starred in five films for Paramount Pictures, including Rose of the Rancho, Give Us This Night and Ambush. For the movie Champagne Waltz with Fred MacMurray, she sang her songs in five languages, including French, German, Italian, and Spanish for the foreign versions of the films.