Arthur Tatum Jr. (, October 13, 1909 – November 5, 1956) was an American jazz pianist.

Tatum grew up in Toledo, Ohio, where he began playing piano professionally and had his own radio program, rebroadcast nationwide, while still in his teens. He left Toledo in 1932 and had residencies as a solo pianist at clubs in major urban centers including New York, Chicago, and Los Angeles. Throughout his career, Tatum also played for long periods at night in after-hours venues – at which he was said to be more spontaneous and creative than in his regular paid performances. Tatum drank large quantities of alcohol when performing, and although it did not negatively affect his playing, it did damage his health. In the 1940s, Tatum led a commercially successful trio for a short time and began playing in more formal jazz concert settings, including at Norman Granz-produced Jazz at the Philharmonic events. Granz recorded Tatum extensively in solo and small group formats in the mid-1950s, with the last session occurring only two months before the pianist's death from uremia at the age of 47.

Tatum is widely regarded as one of the greatest jazz pianists. His playing encompassed the styles of earlier greats, while adding harmonic and rhythmic imagination and complexity. Often playing passages at high velocity, he extended what was considered possible in jazz piano and established new ground in jazz more broadly through innovative use of reharmonization, voicing, and bitonality.