Mareen Louie Harper (neLouie; born August 15, 1960), better known by her nickname Peanut, is a retired American female tennis player, born in San Francisco, California to Ron and Alice Louie. Her elder sister, Marcie, also played on the WTA Tour, while her sisters Cici and Marisa, and brother Ronnie, all played at the University of San Francisco. She, along with her siblings, trained on the tennis courts of Golden Gate Park. She was given the nickname "Peanut" by her dad because she was the youngest of the five children.
Louie Harper won 14 junior national titles and was the top ranked 16-and-under tennis player in the United States in 1976 and top ranked 12-and-under in 1972. She reached the finals of the Wimbledon junior tournament in 1977 and the semifinals in 1978.