Best Ai is the second compilation album by Japanese singer Ai, released on September 16, 2009. The album was released in three editions: limited CD+DVD, CD only and "Arienai Price" (low-priced) editions. Best Ai debuted at number 2 on the daily Oricon albums chart but switched back and forth between number 1 and number 2 several times during its release week. The album went on to debut atop the weekly albums chart with 81,663 copies sold, beating the second-place holder Takeshi Tsuruno's Tsuruno Oto by merely 1,332 units and becoming her first number-one album.