Hasaan Ibn Ali (born William Henry Langford, Jr.; May 6, 1931 – 1980) was an American jazz pianist and composer.

Ibn Ali was strongly influenced by Elmo Hope, and his playing was rapid and intense, retaining a sense of rhythm even when his style became increasingly unconventional. Only one recording of his playing – The Max Roach Trio Featuring the Legendary Hasaan – was released in his lifetime. Ibn Ali built a reputation in Philadelphia, where he influenced musicians including John Coltrane, but he remained little known elsewhere.

Hasaan Ibn Ali was born William Henry Langford, Jr. in Philadelphia on May 6, 1931. His mother was a domestic worker. In 1946 (aged 15), he toured with trumpeter Joe Morris‘s rhythm and blues band. In 1950, he played locally with Clifford Brown, Miles Davis, J. J. Johnson, Max Roach, and others. Based in Philadelphia, Ibn Ali freelanced and acquired a reputation locally as “an original composer and theorist”, in musicologist Lewis Porter‘s words. The pianist performed with Horace Arnold in New York City in 1959, and again in 1961–62, in a trio with Henry Grimes.