Kristen was born on August 22, 1973, in New York.
Wiig moved with her family to Lancaster, Pennsylvania, at the age of three, and attended Nitrauer Elementary School and Manheim Township Middle School until eighth grade.
Her father has Norwegian and Irish ancestry and her mother is of English and Scottish descent.
Wiig has a brother Erik Wiig.
She then moved back to Rochester with her family at the age of 13, where she attended Allendale Columbia School for ninth and tenth grades and graduated from Brighton High School.
Wiig had a brief role in Andrew Jarecki's 2010 drama All Good Things, starred opposite Will Forte and Ryan Phillippe in MacGruber, and provided her voice for two big-budget animated comedies— Despicable Me and How to Train Your Dragon—that would mark the beginning of two highly profitable film franchises.