Witherspoon was born in New Orleans, Louisiana to John Witherspoon, a surgeon from Georgia who grew up in Nashville, and Betty Reese, a nurse and college professor from Harriman, Tennessee. She is a direct descendant of Scottish-born John Witherspoon, a signer of the United States Declaration of Independence and sixth president of Princeton University, who was also a Presbyterian minister. Because her father worked for the US military in Wiesbaden, Germany, she lived there for four years as a small child. After returning to the United States, Witherspoon spent much of her childhood and adolescence in Nashville, Tennessee, where, she says in Interview magazine, "I grew up in an environment where women accomplished a lot. And if they weren't able to it was because they were limited by society. I grew up with a grandma--my father's mother--who was incredibly intelligent but was limited by the bounds of society and propriety ... She was a voracious reader, and she encouraged me to read a lot as a child ..." a woman whose "depression" and "disconnect between her capabilities and her lack of fulfillment and achievement" continues to motivate Witherspoon in life. She has an older brother, John, who works as a real estate broker. After graduating from the prestigious private all-girl's Harpeth Hall School in Nashville, she attended Stanford University as a literature major. After completing a year of her studies, she left Stanford to pursue her acting career.
Witherspoon began her career in local commercials. Her first role was in a 1991 made-for-TV movie called Wildflower, directed by Diane Keaton and starring Beau Bridges, William McNamara, and Patricia Arquette. That same year, at age 14, Witherspoon attended an open casting call for The Man in the Moon, intending to audition as a bit player. She was instead cast in the lead role, immediately capturing the attention of critics. She has since built up an impressive filmography, playing both comedic and dramatic roles, including performances as Vanessa in Freeway and Tracy Flick in Election. She was the voice of the animated character Greta Wolfecastle in The Simpsons episode The Bart Wants What It Wants. She also played Jill Green, Rachel's sister, in season six of "Friends."
She achieved fame and a Golden Globe Best Actress nomination for her role as a fashion designer major who decided to become a law student to follow her ex-boyfriend in the 2001 film Legally Blonde, and became a leading environmental lawyer in its sequel Legally Blonde 2, for which she received a reported $15 million paycheck, making her one of Hollywood's top-paid actresses.
She has garnered critical praise and awards for her turn as June Carter Cash in Walk the Line. Carter Cash, who died in 2003, personally approved of Witherspoon to play her. Witherspoon won the Golden Globe Award for Best Actress " Motion Picture Musical or Comedy, NYFCC, the FFCC, the SFFCC Award for Best Actress, the Screen Actor's Guild (SAG) for best actress in a lead role, the British Academy's BAFTA for best actress in a lead role, the "Favorite Leading Lady" at the 32nd Annual People's Choice Awards, and the Academy Award for Best Actress for this role.
Recently, Witherspoon has been featured as one of Time Magazine's 100 Most Influential People. Her article was written by friend and fellow costar in the Legally Blonde movies, Luke Wilson.
Witherspoon also runs a production company, Type A Productions. Some believe the company is named after her childhood nickname "Little Miss Type A," but she clarified the misconception in Interview: "[P]eople think I named it after myself ... But it just isn't who I am at all. It was actually an in-joke with my family because at 7 I understood complicated medical terms, such as the difference between type A and type B personalities. But I just wished I'd named the company Dogfood Films or Fork or something. You carry that baggage all your life."
Witherspoon has commented on her motivation to act. "Sometimes I think it's about acknowledgment. I always felt like people didn't understand me what I was capable of or what I could accomplish. I was driven to make people understand that I was capable of more ... But for me part of the experience of acting is that it is really moving--it's almost meditative, going into a different character. You lose all self-consciousness and self-awareness for that brief moment. It's really magical. Of course, it can also be drudgery if you can't connect with the material or director." 
Witherspoon met actor Ryan Phillippe at her 21st birthday party in March 1997, where she reportedly said to him, "You must be my birthday present." The pair were engaged in December 1998. Soon after, the couple starred together in the box office hit Cruel Intentions. They were married on a plantation in Charleston, South Carolina on June 5, 1999. They have two children: daughter Ava Elizabeth, born September 9, 1999, and son Deacon, born October 23, 2003. Ava is named after Phillippe's grandmother, and Deacon after one of his distant relatives. Witherspoon and Phillippe have a pact that one of them will always be a full-time parent to the children, and they thus alternate filming schedules. The family resides in Los Angeles, where Witherspoon says she and her children enjoy the good weather outside and which she defends in Interview by proclaiming "people really rag on L.A., and I think it's because they're looking in the wrong places."
Witherspoon is known as a very hands-on mother, and she and her husband claim to have never employed a full-time nanny. A self-identified Southerner who has credited her family with fomenting her imagination and love for storytelling and privacy, she told the aforesaid magazines that her parental philosophy has roots in her upbringing. "We weren't the kind of children that were shadowed. We didn't have nannies. We didn't have housekeepers. This whole L.A. culture is so foreign to me, because when I was growing up you wouldn't watch your children every moment. I'm always confused when people bring their children over and then want to sit with them while they play. I think part of the joy of being a child is privacy. Your fantasies and dreams are so important to you at that moment."
On November 10, 2005 Witherspoon responded to critical news reports of her marriage counseling. "In what capacity is working on yourself or your marriage a bad thing? What marriage isn't a journey? ... Nobody's perfect ... We all have our own set of problems," she said on The Oprah Winfrey Show. The next month, she said separately, "We are all on the edge, emotionally or psychologically."
On June 21, 2006 Witherspoon sued the tabloid Star for running a "fictional" story on a third pregnancy that claims she is hiding the news from producers of her upcoming films.
In September 2005, Witherspoon and her children were celebrating daughter Ava's sixth birthday at Disney's California Adventure theme park when they were approached by paparazzi photographer Todd Wallace. After Witherspoon declined to pose for photos at close range, police say Wallace became enraged and pushed a child out of the way, while hitting another with his camera, in his efforts to photograph the actress.
Wallace also allegedly shoved two theme park employees when they attempted to restrain him, and cursed at Witherspoon, causing several children to burst into tears. As a result of the altercation, Wallace was arrested and faced misdemeanor charges. However, before the case went to trial, Wallace was found dead in his apartment in Brentwood. Police are currently investigating the cause of death.