Rebecca Helferich Clarke (27 August 1886 – 13 October 1979) was a violist and classical composer from the United Kingdom and the United States. She was not only a world-renowned viola virtuoso, but she was also one of the first female professional orchestral musicians. Rebecca Clarke, born in England but claimed both British and American citizenship, spent most of her long life in the United States. She was born in Harrow and attended the Royal Academy of Music and the Royal College of Music in London, where she received her education. She married composer and pianist James Friskin in 1944 after being stranded in the United States at the beginning of World War II. She eventually moved permanently after World War II. Clarke died at the age of 93 in her home in New York. Despite her small output, Clarke's work was praised for its compositional talent and aesthetic force. Some of her compositions have yet to be published (and many have been released lately); those published during her lifetime mainly were forgotten when she ceased writing. In 1976, scholarship and interest in her works resurfaced. In the year 2000, the Rebecca Clarke Society was founded to encourage the study and performance of her music.

She studied with Lionel Tertis, who was widely regarded as the finest violist of his day. In cooperation with a group of other RCM students, she wrote "Tears," a setting of Chinese poetry. She also sang in a student group formed by Clarke to study and perform Palestrina's work under the supervision of Ralph Vaughan Williams. Clarke's father kicked her out of the home and took her money when she criticized his extramarital relationships. She was forced to quit the Royal College in 1910 and supported herself by playing the viola. When Sir Henry Wood chose Clarke to perform in the Queen's Hall Orchestra in 1912, she became one of the first female professional symphonic players. She went to the United States in 1916 to pursue her acting career. Morpheus, a brief lyrical work for viola and piano written under the pseudonym "Anthony Trent" and debuted at her 1918 joint performance with cellist May Muckle in New York City, was written under the pseudonym "Anthony Trent." Reviewers lauded the "Trent," generally disregarding the Clarke pieces that debuted at the same concert. Beginning with a viola sonata she submitted in a 1919 competition sponsored by Elizabeth Sprague Coolidge, Clarke's neighbor and a supporter of the arts, her composing career peaked in a short time.