Kathryn Marie Hahn (born July 23, 1973) is an American actress. She gained prominence appearing as a supporting actress in a number of comedy films, including How to Lose a Guy in 10 Days (2003), Anchorman: The Legend of Ron Burgundy (2004), Step Brothers (2008), Our Idiot Brother (2011), We're the Millers and The Secret Life of Walter Mitty (both 2013), and Glass Onion: A Knives Out Mystery (2022).
As a lead actress in film, Hahn has starred in Joey Soloway's comedy-drama Afternoon Delight (2013), the comedy film Bad Moms (2016) and its sequel A Bad Moms Christmas (2017), and Tamara Jenkins's drama Private Life (2018). Hahn voiced Ericka Van Helsing in two films of the Hotel Transylvania franchise (2018–2022) and Doctor Octopus in Spider-Man: Into the Spider-Verse (2018).
On television, Hahn earned a Primetime Emmy Award nomination for her role in the Amazon series Transparent (2014–2019). She starred in the HBO miniseries Mrs. Fletcher (2019) and I Know This Much Is True (2020) before portraying Agatha Harkness in the Disney+ series WandaVision (2021), a role that earned her Emmy and Golden Globe nominations. Hahn reprised her role as Harkness in the spin-off Agatha All Along (2024). In 2023, she starred in the Hulu series Tiny Beautiful Things, receiving a Primetime Emmy nomination for Outstanding Lead Actress.