Crystal Kay (born Crystal Kay Williams on February 26, 1986 in Yokohama, Kanagawa Prefecture, Japan), is a Japanese recording artist and radio host and actress. She debuted at the age of 13.

After releasing her debut single "Eternal Memories" (1999) 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. 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.