Louise Viktoria Tolstoy (born Louise Viktoria Kjellberg, July 29, 1974 in Sigtuna Municipality, Sweden) is a Swedish jazz singer of Russian ancestry. She is the daughter of Erik Kjellberg and the great-great-granddaughter of Russian writer Leo Tolstoy. Tolstoy was a housemate in season one of the television series Big Brother in 2000.

She was married to designer Per Holknekt from 2001 until they divorced in March 2008.