Allison Lee Hannigan (born March 24, 1974), known professionally as Alyson Hannigan, is an American actress and television presenter.^[1]

Hannigan began her film career with supporting roles in the comedy films Impure Thoughts (1986) and My Stepmother Is an Alien (1988), getting a Young Artist Award nomination for the latter. In 1999, she began starring in the American Pie film series as Michelle Flaherty, the films' primary love interest, appearing in every film in the series from 1999 to 2012. For her role in the series, she was nominated for three Teen Choice Awards and won a Young Hollywood Award. She went on to star in the parody film Date Movie (2006), the slasher film You Might Be the Killer (2018), and the superhero film Flora & Ulysses (2021).

Hannigan got her start in television starring in the short-lived sitcom Free Spirit from 1989 to 1990, for which she earned a Young Artist Award nomination. After several minor roles in television films and other series, she appeared in her breakout role as teenage witch Willow Rosenberg in the supernatural drama series Buffy the Vampire Slayer, appearing in every episode from 1997 to 2003. Her role on the show was critically acclaimed and won her the Saturn Award for Best Supporting Actress on Television and a Teen Choice Award. From 2005 to 2014, she starred as Lily Aldrin in the sitcom How I Met Your Mother, for which she won two People's Choice Awards. Hannigan hosted the television show Penn & Teller: Fool Us (2016–2022), and provided the voice of Claire Clancy in the Disney Junior animated series Fancy Nancy (2018–2022).

Hannigan was born on March 24, 1974^[2] in Washington, D.C., the only child of Emilie (Posner) Haas, a real-estate agent, and Alan Hannigan, a Teamsters trucker.^[3][4] Her father is of Irish ancestry and her mother is Jewish.^[5][6] At age four, Hannigan began appearing in commercials.^[7] After spending her childhood in her mother's hometown of Atlanta, Georgia, Hannigan moved to Hollywood at age 11 after securing an agent.^[4]

Living with her mother and attending North Hollywood High School, she successfully auditioned for agents while visiting her father in Santa Barbara. After high school, she attended California State University, Northridge, where she was a member of the Alpha Chi Omega sorority and earned a degree in psychology.^[8][9]

Hannigan's first major film role was in My Stepmother Is an Alien, a science-fiction comedy released in 1988; one of her co-stars in the film was actor Seth Green, who later joined her in the regular cast of Buffy as her on-screen boyfriend.^[3] In 1989, her first regular role on a TV series came when she was cast in the short-lived ABC sitcom Free Spirit. As a teenager, Hannigan babysat for the children of her future How I Met Your Mother co-star, Bob Saget.^[10]

In 1997, Hannigan was cast to play Willow Rosenberg, Buffy Summers' best friend, on the television series Buffy the Vampire Slayer.^[11] The show became a success, and Hannigan gained recognition, subsequently appearing in several films aimed at teenaged audiences, including American Pie (1999), Boys and Girls (2000), American Pie 2 (2001), and American Wedding (2003).^[3] She also had a recurring guest spot on the Buffy spin-off, Angel, reprising her role of Willow. In early 2004, Hannigan made her West End debut, starring in a stage adaptation of When Harry Met Sally... at the Theatre Royal Haymarket, opposite Luke Perry.^[12]

In 2005, Hannigan returned to starring in a regular television series, taking the main role of Lily Aldrin in the hit comedy How I Met Your Mother, and also playing a recurring guest role on Veronica Mars as Trina Echolls.^[13] In February 2006, she starred as Julia Jones in Date Movie, a parody of romantic comedies.^[3] She was also a guest star on the ABC animated sitcom The Goode Family in 2009.^[14]

Hannigan joined forces with Emily Deschanel, Jaime King, Minka Kelly, and Katharine McPhee in a "video slumber party" featured on FunnyorDie.com to promote regular breast cancer screenings for the organization Stand Up 2 Cancer.^[15] In 2012, Hannigan reprised the role of Michelle in American Reunion.^[16] From 2016 to 2022, Hannigan hosted the television series Penn & Teller: Fool Us.^[17] Hannigan played Ann Possible, Kim's mother, in the Disney Channel original film Kim Possible, based on the animated series.^[18]

In September 2023, Hannigan was announced to be competing on season 32 of Dancing with the Stars, partnering with Sasha Farber.^[19] The couple made it to the finals and finished in fifth place.

Hannigan married her Buffy the Vampire Slayer and Angel co-star Alexis Denisof at Two Bunch Palms Resort in Desert Hot Springs, California, on October 11, 2003. The couple live in Encino, Los Angeles^[20] with their two daughters.^[2][21] Their home was used as a set for This Is Us.^[22]

Hannigan is a fan of singer Taylor Swift.^[23]