Ashlee Nicole Wentz (born October 3, 1984), is an American recording artist and actress. Simpson, who is the younger sister of pop singer Jessica Simpson, rose to prominence in mid-2004 through the success of her number-one debut album Autobiography and the accompanying reality series The Ashlee Simpson Show. Simpson received widespread notoriety when she attempted to lip-sync with a pre-recorded vocal track on Saturday Night Live in October 2004. Following a North American concert tour and a film appearance, Simpson released a second number-one album, I Am Me, in October 2005. Her third album, Bittersweet World, was released in April 2008. The following month, she married musician Pete Wentz and announced that they were expecting a child. On November 20, 2008, Simpson gave birth to their son, Bronx Mowgli Wentz. Simpson filed for divorce on February 8, 2011, citing "irreconcilable differences." Simpson was born in Waco, Texas, and raised in Richardson, Texas. She is the second daughter of Tina Ann (née Drew) and Joe Truett Simpson, a former Baptist youth minister who is now her manager. She attended Prairie Creek Elementary. Simpson began studying classical ballet at the age of three. She eventually became an accomplished dancer and was admitted to the School of American Ballet in New York City at the age of 11, a year in advance. Around that time, she suffered from an eating disorder; the condition lasted about six months, but her parents then stepped in and got her the help she needed to overcome the issue. After her sister Jessica Simpson landed a record deal, the Simpson family decided to move to Los Angeles, California, where Ashlee began appearing in television commercials.

When her older sister Jessica became a star after releasing her first album, Ashlee became one of her backup dancers. Later, Ashlee began appearing in films and television series, including an episode of the sitcom Malcolm in the Middle in 2001, a minor role in the 2002 film The Hot Chick and a recurring role, 39 episodes from 2002–2004, on the family drama series 7th Heaven. Simpson recorded a song called "Christmas Past, Present and Future" in 2002 for the holiday album School's Out! Christmas, later to be re-released on Radio Disney Jingle Jams in 2004 and 2005. On March 18, 2009, Simpson-Wentz appeared alongside her husband in the crime drama series CSI: NY. She played a drug dealer named Lila Wickfield in Season 5, Episode 18, "Point of No Return". This marked Simpson-Wentz first acting role since her stint in the 2006 west end production Chicago. Simpson returned to television in the acting role of Violet Foster in Melrose Place, the CW's revamp of the '90s series Melrose Place. Simpson was originally signed to the show as a full-fledged cast member, but producers and CW executives changed their mind and Simpson was let go from the show after 13 episodes. Multiple rumors surfaced about her sudden departure, including feuds with cast members, lack of acting ability and financial issues.

Simpson-Wentz stated that she knew all along that her character would be written out once the murder mystery storyline had concluded. Her last appearance on the show aired in March 2010. It was later revealed that Simpson's departure was due to the show needing a "face lift" because of the decreasing viewing figures. It was reported on November 5, 2009, that Simpson-Wentz would reprise her role in the Broadway musical production Chicago. It was later confirmed on November 16, 2009. She began her Broadway run on November 30, 2009 and performed in New York for six weeks. She played 8 shows a week through February 7, 2010. After finishing her run in Chicago Simpson-Wentz stated in an interview that she was going to take a break to spend time with her son. She also stated that she is ready to record her fourth studio album, and has been listening to bands on her husband's record label for inspiration. She did however say she will continue acting, but wishes to play comedy roles in the future. At a red carpet event, Simpson confirmed that she is back in the recording studio working on her fourth album. During an interview with Paper magazine, Simpson-Wentz stated that the new album would have a “folk feel” and that she is also creating a fashion line.

Simpson cites her childhood as being the time when she began to sing, and admits that she dreamed of being on Broadway and didn't expect to break into the pop music scene. Simpson trains with a vocal coach, and studies old Etta James and Aretha Franklin albums for vocal inspiration. In one interview, Simpson pointed to Joan Jett, The Runaways, Madonna, Pat Benatar, Chrissie Hynde, and Debbie Harry from Blondie as musical influences. Simpson cited that she is a fan of several musicians and bands which include Alanis Morissette, Fiona Apple, Green Day, Björk, Joan Osborne, Karen O from the Yeah Yeah Yeahs, and Gwen Stefani. When Simpson first broke onto the music scene in 2004, she was set apart from her sister's already established image by a different musical style, different fashion choices, and a more assertive personality. Simpson's songs have been characterized by rock elements absent from her sister's music, and, particularly during the time of her initial stardom, Simpson would often wear outfits highlighting a more rock or punk-influenced sense of style. Her fingernails and toenails have often been painted black. Over time, Simpson has moved toward more typically feminine styles. In March 2008, she said that "I like to get dressed up now, and that's something I've never been into before" and "I like to be feminine and sexy."

According to Simpson, in her sense of style she tends to "mix and match". Previously blonde like Jessica, she dyed her hair dark during the recording of the MTV reality show after she finished filming for the 7th Heaven television series. In November 2004, she debuted a shorter haircut with the same dark color. Following the end of her Autobiography tour, in early May 2005 she moved back to a blonde color; she remained blonde until January 2008, when she appeared with a red hair color. During her stint on Broadway, she dyed her hair black. Recently, she dyed her hair back to a bleached blonde paired with a pixie cut. She has seven tattoos, including a star tattoo on one wrist, two cherries on her ankle, the word "love" on her other wrist, the number "3" added to one wrist in 2007, and a large peony flower on one wrist in early March 2008. In November 2005, eTalk broadcast a video of a late-night visit made by Simpson to a McDonald's fast-food restaurant in Toronto, Canada. Simpson appeared to be intoxicated in the video, and was shown arguing with an employee, as well as rejecting a customer's attempt to get an autograph from her because he wouldn't kiss her feet. According to Simpson in a 2006 Elle interview, she was "a little tipsy", and the customer had first called her "gross" before he had realized who she was, at which point he asked her for an autograph. She said that she told herself to "grow up" after the incident.

On May 28, 2008, Simpson and Pete Wentz announced on Fall Out Boy's official website that they were expecting their first child. "While many have speculated about this, we wanted to wait until the press was gone to have our first child. This is truly the most joyous time in our lives and we are excited to share the happy news and start our family." That fall, Pete said they were "90% sure it was a boy". On November 20, 2008, Simpson gave birth to their son, Bronx Mowgli Wentz. Simpson was ranked in the Billboard Decade-End Chart at #145 of Billboard 200 artists, while Autobiography was ranked at #148 on the Billboard 200 Albums. On February 9, 2011, it was announced that Simpson had filed for divorce from husband Pete Wentz, citing irreconcilable differences. In the filing she asked for joint legal custody with visitation for Wentz but sole physical custody and spousal support. She also asked that her name be restored to her birth name of Ashlee Nicole Simpson. Jenny Eliscu of Rolling Stone magazine criticized Simpson as being a "manufactured" artist with little singing talent. Simpson's critics cite incidents like the SNL episode and the Orange Bowl performance as evidence for their claims. In mid-2006, Simpson gave an interview to Marie Claire magazine, in which she was said to have "had it with Hollywood's twisted view of feminine beauty" and was photographed painting a pro-female mural with a group of underprivileged girls from Los Angeles' Green Dot Public School. By the time the magazine hit newsstands, Simpson had already had her nose job, and some Marie Claire readers complained about this as being hypocritical. The magazine received over 1,000 angry letters and the magazine's new editor expanded the letters section of the September issue of the magazine to give readers a chance to vent their frustrations.