Kristen Carroll Wiig was born on August 22, 1973 in Canandaigua, New York, to Laurie J. (Johnston), an artist, and Jon J. Wiig, a lake marina manager. She is of Norwegian (from her paternal grandfather), Irish, English, and Scottish descent. The family moved to Lancaster, Pennsylvania, before settling in Rochester, New York. When Wiig was 9 years old, her parents divorced and she lived with her mother and older brother Erik.
After graduating from Brighton High School in Rochester, Wiig attended the University of Arizona as an art student. She took her first acting class, as an elective, and was soon encouraged by her teacher to pursue acting. Years later, she moved to Los Angeles and Wiig worked as a main company member of the Los Angeles-based improv and sketch-comedy troupe The Groundlings. As a Groundlings alumna, she joins the ranks of such SNL cast mates as Maya Rudolph, Will Ferrell, Phil Hartman, and Jon Lovitz.