Mary Lou Williams was a pioneering American jazz pianist, composer, and arranger who left an indelible mark on the genre. Her career spanned from the 1920s swing era to the 1970s, during which she wrote hundreds of compositions for iconic bandleaders like Duke Ellington and Benny Goodman. A true innovator, she mentored many younger musicians, including Thelonious Monk and Dizzy Gillespie, influencing the development of bebop. Later in her life, she dedicated herself to sacred jazz music, composing several masses and continuing to perform and teach until her passing.