Alyson Hannigan

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 (2016–2023), and provided the voice of Claire Clancy in the Disney Junior animated series Fancy Nancy (2018–2022).

Hannigan was born on March 24, 1974 in Washington, D.C., the only child of Emilie (Posner) Haas, a real-estate agent, and Alan Hannigan, a Teamsters trucker. Her father is of Irish ancestry and her mother is Jewish. At age four, Hannigan began appearing in commercials. After spending her childhood in her mother's hometown of Atlanta, Georgia, Hannigan moved to Hollywood at age 11 after securing an agent. As a teenager, Hannigan babysat for the children of her future How I Met Your Mother co-star, Bob Saget. 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.

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 the Vampire Slayer as her on-screen boyfriend. In 1989, her first regular role on a television series came when she was cast in the short-lived ABC sitcom Free Spirit. In 1997, Hannigan was cast to play Willow Rosenberg, Buffy Summers' best friend, on the supernatural television series Buffy the Vampire Slayer. The show became a success, and Hannigan gained recognition, subsequently appearing in several films aimed at teenage audiences, including Boys and Girls (2000). She had a supporting role as Michelle Flaherty in the comedy film American Pie (1999), and appeared in a much larger role in its sequels American Pie 2 (2001) and American Wedding (2003). In 2017, Forbes reported that the American Pie films have grossed $989.5 million at the worldwide box office, and became a pop culture phenomenon. She also had a recurring guest spot on the Buffy the Vampire Slayer 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.

In early 2005, she had a recurring guest role as Trina Echolls in three episodes of UPN's teen mystery series Veronica Mars. In September 2005, Hannigan returned to starring in a regular television series, taking the main role of Lily Aldrin in CBS's sitcom How I Met Your Mother. The series followed architect Ted Mosby and his group of friends in New York City. Ted recounts to his children the events that led him to meet their mother. Hannigan's character Lily was a kindergarten teacher and amateur painter, who eventually married lawyer Marshall Eriksen, portrayed by Jason Segel. Hannigan won the People's Choice Award for Favorite TV Comedy Actress in 2010. Known for its unique structure, humor, and incorporation of dramatic elements, How I Met Your Mother was popular throughout its run. The series ran for nine seasons and the one-hour series finale aired on March 31, 2014. In February 2006, she starred as Julia Jones in Date Movie, a parody of romantic comedies. She was also a guest star on the ABC animated sitcom The Goode Family in 2009. 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. Hannigan reprised the role of Michelle in the comedy film American Reunion (2012). The film followed the friends attending a high school reunion thirteen years after graduating from high school. The film was a success at the box office, and grossed $235 million worldwide. For her role in the film, she was nominated for Choice Movie Actress: Romantic Comedy award at the 2012 Teen Choice Awards.

Hannigan hosted the television series Penn & Teller: Fool Us from 2016 to 2023. Hannigan played Ann Possible, Kim's mother, in the Disney Channel original film Kim Possible (2019), based on the animated series. She voiced the role of Claire Nancy in Disney Junior's animated series Fancy Nancy (2018–2022). The show ran for three seasons, and the series finale aired on February 18, 2022. In September 2023, Hannigan was announced as one of the contestants on season 32 of Dancing with the Stars, partnering with Sasha Farber. The couple made it to the finals and finished in fifth place. Hannigan played a supporting role in the 2026 romantic comedy Solo Mio.

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, with their two daughters. Their home was used as a set for This Is Us.