Alison Margaret Arngrim (born January 18, 1962) is a Canadian-American actress and author. Beginning her television career at the age of twelve, Arngrim is a Young Artist Award–Former Child Star "Lifetime Achievement" Award honoree, best known for her portrayal of Nellie Oleson on the NBC television series Little House on the Prairie from 1974 to 1981.
Arngrim's father, Thor Arngrim, was a Canadian-born Hollywood manager. Her mother, Norma MacMillan of Vancouver, British Columbia, was an actress who provided the voices for characters as Casper on Casper the Friendly Ghost, as Gumby on Gumby, as Davey on Davey and Goliath, and Sweet Polly Purebred on Underdog, as well as other animated children's programs.
Her brother, Stefan (b. 1955) was also a child actor, perhaps best known for his role as Barry Lockridge on the Irwin Allen science fiction television series, Land of the Giants. Arngrim has claimed that her brother sexually molested her from age six until nine.