Catherine Cartan "CiCi" Bellis (born April 8, 1999) is an American tennis player.Bellis has won two singles and one doubles title on the ITF tour in her career. On January 12, 2015, she reached her best singles ranking of world number 251. On January 5, 2015, she peaked at world number 811 in the doubles rankings.Bellis was ranked the number one junior tennis player in the world in September 2014, and was declared 2014 ITF Junior World Champion.In August 2014, Bellis won the USTA Girls 18's National Championships, defeating Tornado Alicia Black in straight sets to secure a main draw wild card for the 2014 US Open. She was the youngest winner of that event since Lindsay Davenport in 1991.On August 26, 2014, Bellis defeated former Australian Open runner-up Dominika Cibulková (ranked 13th at the time) at the 2014 US Open, becoming the youngest player to win a match at the US Open since Anna Kournikova won aged 15 in 1996. She was the youngest American to win a match at the US Open since Mary Joe Fernández in 1986, the youngest woman in the main draw of a Grand Slam since Alizé Cornet at the 2005 French Open and youngest in the main draw of the US Open since 2004. Bellis was unable to win a second match, however, losing in three sets to the 20-year old Kazakhstani Zarina Diyas in round two.