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 album, Kun valaistun, was released on October 5, 2011, through Warner Music Finland. Another version of the album, entitled Kun valaistun 2.0 was released on June 6, 2012. Her fourth and latest album, Polaris was released on October 2, 2015.