Phoebe Palmer Knapp (March 9, 1839 – July 10, 1908) was an influential American composer of hymn music and an organist. Born in New York City to Walter C. Palmer and Phoebe Worrall Palmer, she demonstrated musical talent from a young age, composing and singing children's songs. At sixteen, she married Joseph Fairchild Knapp, a founder of the Metropolitan Life Insurance Company. The couple were active members of the John Street Methodist Episcopal Church in New York City, where Knapp developed a close friendship with hymn writer Fanny Crosby.

Knapp composed over 500 hymn tunes, with her most enduring work being the melody for "Blessed Assurance," set to lyrics by Fanny Crosby. Other notable collaborations with Crosby include "Open the Gates of the Temple" and "Nearer the Cross." Her compositions also include tunes like "Albertson," "Consecration," and several sacred choral and solo works. Knapp's first published collection, "Notes of Joy" (1869), contained 100 original pieces and gained wide popularity.

Beyond her musical contributions, Knapp was a prominent social leader and philanthropist, using her wealth to support various charitable causes. She passed away in Poland, Maine, leaving behind a legacy of beloved gospel music that continues to inspire.