Kjartan "Kjarri" Sveinsson is a keyboardist of the Icelandic post-rock band Sigur Rós. He joined the band in 1998. Being something of a multi-instrumentalist, he has also played such instruments as the flute, tin whistle, oboe and even the banjo, as well as many of the unorthodox instruments that contribute to Sigur Rós's distinctive sound. He also plays the guitar.