Kerkko Klemetti Koskinen (born 7 January 1973 in Espoo) is a Finnish musician.
Koskinen was the founding member and lead figure of the retired band Ultra Bra.
He composed nearly all of Ultra Bra's songs and was the band's pianist.
His most well-known solo songs are "Rakkaus viiltää" ("Love Cuts") and "Sateentekijä" ("Rainmaker").
Koskinen has worked as a talent scout for BMG and composed music for the Finnish films Upswing and Young Gods.
He also composed songs for Vuokko Hovatta's solo album Lempieläimiä, one of which was a Eurovision Song Contest candidate called "Virginia".
Furthermore, Koskinen wrote the song "Uuden ajan kynnyksellä" ("At the Threshold of a New Time") in memory of the murder of reporter Anna Politkovskaya.