Crystal Kay Williams (クリスタル・ケイ・ウィリアムズ, Kurisutaru Kei Wiriamuzu?) (born February 26, 1986), better known by her stage name Crystal Kay (クリスタル・ケイ, Kurisutaru Kei?), is a Japanese singer and songwriter from Yokohama, Kanagawa, Japan. After releasing her debut single "Eternal Memories" (1999) Kay gained fame for her third studio album, Almost Seventeen (2002), which debuted at number-two on the Japanese Oricon charts. Almost Seventeen eventually sold over 400,000 copies and was certified platinum by the Recording Industry Association of Japan. Kay is currently signed to Epic Records, a sub-label of Sony Music Japan.
As of July 2009, Kay has released ten albums. Her seventh studio album, All Yours (2007) became Kay's first number-one release in her career when it debuted on top of the Oricon chart in June 2007. Kay has sold over two million records in Japan as of 2009. Throughout her career, Kay has collaborated with the likes of M-Flo and BoA, Chemistry as well as other well-known recording artists.