Christel Martina Sundberg (born January 3, 1982, Helsinki), known by her stage name Chisu, is a Finnish pop artist, songwriter, and producer. She wrote her first single, "Mun koti ei oo täällä", to the soundtrack of the movie Sooloilua. The song was a hit in Finland in Spring 2008, peaking at number one on both the Singles Chart and the Downloads Chart and spending seven and nine weeks atop, respectively. She released her second album Vapaa ja yksin on September 23, 2009. Her third and latest album, Kun valaistun, was released on October 5, 2011, through Warner Music Finland.
Chisu has also written songs for Antti Tuisku, Tarja Turunen, Jippu, Kristiina Brask and Kristiina Wheeler. During her career, Chisu has sold over 210,000 certified records, which places her among the top 90 best-selling artists in Finland.
In November 2012, Chisu was connected to a copyright controversy in Finland when a nine-year-old girl's home was raided by the police and had her laptop confiscated due to allegedly downloading Chisu songs. The controversy was named as Chisugate by media.