Hilary Erhard Duff (born September 28, 1987) is an American actress, singer, songwriter, businesswoman, and author. Duff began her acting career at a young age and quickly became labeled a teen idol as the title character of the Disney Channel television series Lizzie McGuire (2001–2004) and in the theatrical film based off the series, The Lizzie McGuire Movie (2003). Thereafter, Duff appeared in numerous films, with leading roles in Agent Cody Banks (2003), Cheaper by the Dozen (2003), A Cinderella Story (2004), and Cheaper by the Dozen 2 (2005). After experiencing commercial and critical failure in Material Girls (2006), Duff began appearing in independent films such as War, Inc. (2008), According to Greta (2009), and Bloodworth (2010). Since 2015, she has starred as Kelsey Peters on the TV Land comedy-drama series Younger, for which she has received nominations for People's Choice Awards in 2016 and 2017.
Duff first came to prominence in music after releasing her Christmas-themed debut studio album Santa Claus Lane (2002) through Walt Disney Records. She then enjoyed significant commercial success and platinum and gold certifications with her subsequent studio albums released through Hollywood Records, including Metamorphosis (2003), Hilary Duff (2004), Most Wanted (2005), and Dignity (2007). Following a hiatus from music, Duff signed with RCA Records for her fifth studio album Breathe In. Breathe Out. (2015), which debuted in the top 5 positions in North America. In addition to music and acting, Duff has also co-authored a trilogy of novels, beginning with Elixir (2010), which became a New York Times best seller, and followed by the sequels Devoted (2011) and True (2013).
Duff's success in both acting and music has led to her becoming a household name, also seeing success with merchandise such as dolls, clothing, and fragrances. She has also had fashion lines of her own such as Stuff by Duff, Femme for DKNY and most recently "The Muse x Hilary Duff" collection, a collaborative effort with GlassesUSA.com. She has been the subject of media attention throughout her career, with interest focusing on her romantic relationships, friendships, and public image, especially her relationships with Aaron Carter and Joel Madden when she was a teenager. Duff was married to former professional hockey player Mike Comrie from 2010 to 2016, with whom she shares a son. Duff has been described as an inspiration by subsequent Disney teen stars such as Miley Cyrus, Demi Lovato, and Selena Gomez, and has sold an estimated 15 million records since her debut in 2002.