Eileen Farrell (February 13, 1920 – March 23, 2002) was an American soprano who had a nearly 60-year-long career performing both classical and popular music in concerts, theatres, on radio and television, and on disc. NPR noted, "She possessed one of the largest and most radiant operatic voices of the 20th century." While she was active as an opera singer, her concert engagements far outnumbered her theatrical appearances. Her career was mainly based in the United States, although she did perform internationally. The Daily Telegraph stated that she "was one of the finest American sopranos of the 20th century; she had a voice of magnificent proportions which she used with both acumen and artistry in a wide variety of roles", and described her as having a voice "like some unparalleled phenomenon of nature. She is to singers what Niagara is to waterfalls."

Farrell began her career in 1940 as a member of the CBS Chorus on CBS Radio. In 1941, CBS Radio offered Farrell her own program, Eileen Farrell Sings, on which she performed both classical and popular music for five years. In 1947 she launched her career as a concert soprano and nine years later began performing on the opera stage. The pinnacle of her opera career was five seasons performing at the Metropolitan Opera from 1960 to 1966. She continued to perform and record both classical and popular music throughout her career, and is credited for releasing the first successful crossover album: I've Got a Right to Sing the Blues (1960). After announcing her retirement from performance in 1986, she still continued to perform and record music periodically up into the late 1990s. She was also active as a voice teacher, both privately and for nine years at Indiana University.

Farrell was born in Willimantic, Connecticut, United States, the youngest of three children born to Irish American Catholics Michael Farrell and Catherine Farrell (née Kennedy). Her parents were vaudeville singers who had performed under the name "The Singing O'Farrells" prior to having children. The family moved quite frequently during Farrell's childhood to various towns in Connecticut. Eileen's first clear memories were of her family's home in Storrs, Connecticut, which was where her parents were working as teachers of music and drama at Storrs Agricultural College (now the University of Connecticut).

When Farrell was five years old, her family moved back to Willimantic. After she attended first grade there, her family moved once again to Norwich, Connecticut, after her mother obtained the post of organist at St. Mary's Church in that city. The family remained in Norwich for almost the next 10 years, with Farrell completing her freshman year of high school at Norwich Free Academy in 1935. The family then moved to Woonsocket, Rhode Island, and in the Fall of 1936 Farrell entered Woonsocket High School, from which she graduated in 1939.

Farrell received her early vocal training from her parents during her childhood. Her mother, a talented coloratura soprano, was her primary teacher, but her father, a baritone, also occasionally taught her. Miss Farrell's early singing career was greatly encouraged by her local pastor, Father Cornelius J. Holland, at St. Charles Borromeo Church in Woonsocket, Rhode Island. After graduating from high school, she moved to New York City in August 1939 to study with retired Metropolitan Opera contralto Merle Alcock. While studying singing with Alcock, she received language coaching from Charlie Baker, who was the music director of Rutgers Presbyterian Church. After she had worked with him for a few months, he hired her as a paid singer at Rutgers. When her radio career took off, Baker became Farrell's vocal coach and helped her prepare most of her music. In her autobiography, Can't Help Singing: The Life of Eileen Farrell (1999), she credits Baker with helping her succeed during the early years of her career on radio. Farrell later was a student of vocal and opera coach Eleanor McLellan, whom she credited for giving her a solid technique.

In 1940, Farrell began her career as a member of the CBS Chorus. After three months with the chorus, CBS offered her a weekly half-hour radio program, Eileen Farrell Sings (also sometimes called Eileen Farrell Presents), on which she would perform both classical and popular music accompanied by the CBS Orchestra under conductor Howard Barlow. The program was coordinated by music director Jim Fassett and was mostly recorded at what is now the Ed Sullivan Theater. On the program she got to sing with several notable guest artists, including Margaret Harshaw, Frank Sinatra, Martial Singher, and Risë Stevens. The program first aired in early 1941 and quickly became popular. It ran through 1946.

While singing on her own program, Farrell also appeared as a guest on several other radio programs. She was a regular guest on Andre Kostelanetz's The Pause That Refreshes and Bernard Herrmann's Invitation to Music. She also made appearances on The Bell Telephone Hour, The Prudential Family Hour, Songs of the Centuries, and Your Hit Parade, among others. In 1944, she made a special Christmas recording that was for the American soldiers stationed abroad during World War II, with Shirley Temple as mistress of ceremonies.

During 1947–1948, Farrell toured the US as a concert singer, and in 1949 she toured South America.