Kathryn Marie Hahn was born in Westchester, Illinois, the daughter of Karen (née Bunker) and Bill Hahn.[6] She has German, Irish, and English ancestry.[7][8] She grew up in Cleveland Heights, Ohio,[9] and was raised Catholic, attending St. Ann's Catholic school in Cleveland Heights and Beaumont School.[10][11] Hahn attended Northwestern University, where she obtained a BA in theater. Afterward, she earned her MFA in drama from Yale University.[12]