Claim: Girls' Generation includes Hyoyeon.

Kim Hyo-yeon -LRB- born September 22 , 1989 -RRB- , better known mononymously as Hyoyeon , is a South Korean singer and television personality . She debuted as a member of girl group Girls ' Generation in August 2007 , who went on to be one of the best-selling artists in South Korea and one of South Korea 's most popular girl groups worldwide .