Crystal Kay Williams (クリスタル・ケイ・ウィリアムズ, Kurisutaru Kei Wiriamuzu, born February 26, 1986) is a Japanese singer, songwriter, actress and radio host.

After releasing her debut single “Eternal Memories” (1999), Crystal Kay gained fame for her third studio album, Almost Seventeen (2002), which debuted at number 2 on the Japanese Oricon charts. Almost Seventeen eventually sold over 400,000 copies and was certified platinum by the Recording Industry Association of Japan. Crystal Kay, formerly signed to Epic Records, a sub-label of Sony Music Japan for 12 years, suddenly transferred to Delicious Deli Records, a sub-label of Universal Music Japan in 2011.