See her autobiography, Such Sweet Compulsion (1938).
Farrar was born in Melrose, Massachusetts, the daughter of Sidney Farrar and his wife Henrietta Barnes. She studied voice in Boston, New York, Paris and finally in Berlin with famed soprano Lilli Lehmann. (She had been recommended to Lehmann by another famous soprano of the previous generation, Lillian Nordica.) Farrar created a sensation in the German capital with her debut as Marguerite in Gounod's Faust in 1901. She appeared subsequently in the title rôles of Thomas' Mignon and Massenet's Manon, as well as Juliette in Gounod's Roméo et Juliette. Among her admirers in Berlin was Crown Prince Wilhelm of Germany, with whom she is believed to have conducted a romantic liaison beginning in 1903.
After appearing at Monte Carlo, she made her debut at the New York Metropolitan Opera in Romeo et Juliette in 1906. She appeared in the first Met performance of Puccini's Madama Butterfly in 1907 and remained a member of the company until her retirement in 1922, singing 29 roles there in nearly 500 performances. She developed a great popular following, especially among New York's young female opera-goers, who were known as 'Gerry-flappers'.
Farrar created the title roles in Mascagni's Amica (Monte-Carlo, 1905), Puccini's Suor Angelica (New York, 1918), and Giordano's Madame Sans-Gêne (New York, 1915) as well as the Goosegirl in Humperdinck's Die Königskinder (New York 1910)
She was, in best opera diva style, noted for her firey temper and fiercely independent nature. She recorded extensively for the Victor Talking Machine Company and was often featured prominently in that firm's advertisements (an example can be seen at 1914 in music). She also appeared in silent movies, which were filmed between opera seasons. Farrar starred in more than a dozen films from 1915 to 1920, including Cecil B. De Mille's 1915 adaptation of Bizet's opera Carmen. Perhaps her most notable screen role was as Joan of Arc in the 1917 film Joan the Woman.
Farrar had a seven-year love affair with the great Italian conductor Arturo Toscanini. Her ultimatim, that he leave his wife and marry her, resulted in Toscanini's resignation as chief conductor of the Met in 1915. He returned to Italy. Farrar was close friends with the star tenor Enrico Caruso and there has been speculation that they too had a love affair; but no substantial evidence of this has surfaced.
Her marriage to cinema actor Lou Tellegen on February 8, 1916 was the source of considerable scandal, terminating, as a result of her husband's numerous affairs, in a very public divorce in 1923. The circumstances of the divorce were brought again to public recollection by Tellegen's bizarre 1934 suicide in Hollywood.
Farrar retired from opera in 1922 at the age of 40. Her final performance was as Leoncavallo's Zaza. By this stage, her voice was in premature decline due to overwork. According to the American music critic Henry Pleasants, the author of The Great Singers from the Dawn of Opera to Our Own Time (first published 1967), she gave between 25 and 35 performances each season at the Met alone. They included 95 appearances as Madama Butterfly and 58 as Carmen in 16 seasons. The title role in Puccini's Tosca, which she had added to her repertoire in 1909, was another one of her favourite Met parts.
Farrar continued to give recitals until 1931 and was briefly the commentator for the radio broadcasts from the Met during the 1934-35 season. Her autobiography, Such Sweet Compulsion, published in 1938, was written in alternating chapters purporting to be her own words and those of her mother, with Mrs Farrar rather floridly recounting her daughter's many accomplishments.
Farrar died in Ridgefield, Connecticut of a heart attack in 1967, aged 85, and was buried in Kensico Cemetery in Valhalla, New York. She had no children. Her voice lives on, however, in the recordings which she made in Europe and America prior to World War One. These recordings are now available on a variety of CDs.