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.

“Reckless with his health, Hasaan died young”, commented writer Geoffrey Haydon in 2002. The New Grove Dictionary of Jazzstates that Ibn Ali died in Philadelphia in 1980 (aged 48 or 49). Ibn Ali’s parents had been killed in a fire that destroyed their home at 2406 North Gratz Street on October 24 that year. He went to a recreation centre for homeless people after the fire.