April Jeanette Mendez was born on March 19, 1987, in Union City, New Jersey. Her mother, Janet Acevedo, was a homemaker and later a home health aide, while her father, Robert Mendez, was an automotive engineer. She is the youngest of three children, and of Puerto Rican descent. In describing her childhood, Mendez said her family struggled with poverty, mental illness, and drug addiction. They frequently moved between apartments, sometimes living in motels or their car when they could not afford rent.

Her brother’s interest in World Wrestling Entertainment (WWE) influenced her to become a professional wrestler. With inspiration from WWE’s female wrestlers, especially Lita, she cemented her ambition at twelve years old. In 2005, Mendez graduated from Memorial High School in West New York, New Jersey. She attended New York University’s Tisch School of the Arts in New York City, where she majored in film and television production, until family and financial issues led to her dropping out six months into her studies. Afterward, she started working full-time to afford wrestling training. As an homage to her brother, who was in the U.S. Army, she once wore camouflage wrestling attire.

In March 2007, Mendez enrolled in a wrestling school close to her home, where she was trained by Jay Lethal. Around late 2007, she began to perform on the New Jersey independent circuit under the ring name Miss April. She joined the New Jersey-based promotion Women Superstars Uncensored (WSU) in October 2008. After little success in her first months, Miss April formed a tag team with Brooke Carter, who together captured the WSU Tag Team Championship in February 2009. She also won the annual WSU/National Wrestling Superstars King and Queen of the Ring tournament alongside Jay Lethal two months later. In May, she left WSU upon signing with WWE and relinquished her championship.

Mendez paid US$1,500 to attend a WWE tryout camp in May 2009, where she signed a contract. She reported to Florida Championship Wrestling (FCW), WWE’s developmental territory, and debuted under the ring name April Lee at a house show in late July. Shortly thereafter, her name was changed to AJ Lee. In February 2010, AJ defeated Serena Mancini to win the Queen of FCW title. A few months later, AJ was eliminated from a tournament that determined the inaugural FCW Divas Champion; she engaged in a feud with the winner, Naomi Knight, and her character became a heel (bad guy). In November, AJ lost the Queen of FCW title to Rosa Mendes. AJ then defeated Naomi for the FCW Divas Championship in December, which made her the first to win both titles available to FCW’s female wrestlers. She held the championship until April 2011, when she lost it to Aksana.

While in FCW, Mendez took part in the third season of NXT beginning in September 2010. The show mixed professional wrestling and reality competition formats as six female participants from FCW competed to be WWE’s “next breakout star”. Primo was assigned as her “WWE Pro”, the role of her mentor in the storyline. She performed as a face (good guy) on the show and WWE adapted her “nerd” fandom to her character. Throughout the season, a relationship between AJ and Primo was teased, with them ultimately kissing on the finale. She also developed an on-screen friendship with fellow competitor, Kaitlyn. On November 23, AJ was eliminated in third place.

By November 2011, AJ was placed in an on-screen romance with Daniel Bryan, who won the World Heavyweight Championship the next month and developed heel traits. Despite AJ’s declaration of love for Bryan, Bryan avoided saying he loved her in return. On January 13, 2012, while accompanying Bryan for his title defense, she was accidentally struck by Big Show and carried off on a stretcher as part of the storyline. She returned on February 3, preventing Bryan from being attacked by Big Show. In March, Bryan started acting verbally abusive towards AJ but she stood by him. At WrestleMania XXVIII on April 1, after sharing a “good luck kiss” with Bryan, he was surprised by Sheamus and defeated in 18 seconds. Bryan blamed AJ for his loss of the World Heavyweight Championship and ended their relationship. AJ made multiple attempts to mend their relationship but Bryan spurned her and left her distraught. As a result, she attacked Natalya and Kaitlyn when they attempted to comfort her, marking her character’s transition to “mentally unstable”.

In 2012, Mendez became the first female winner of WWE’s annual Superstar Challenge video game tournament, where sixteen wrestlers competed in WWE ’12 at WrestleMania XXVIII Axxess. This is recognized by Guinness World Records, as part of their Gamer’s Edition. Her WWE character was portrayed by Thea Trinidad in the 2019 film Fighting with My Family.

In March 2013, AJ’s storyline rivalry with ex-boyfriend Daniel Bryan was reignited when they traded insults backstage. She and Langston assisted Ziggler in victories over Bryan and his tag team partner Kane, which led to Ziggler and Langston losing to them in a WWE Tag Team Championship match at WrestleMania 29 on April 7, despite her interference. The next night on Raw, she and Langston accompanied Ziggler as he cashed in his Money in the Bank contract on Alberto Del Rio to win the World Heavyweight Championship.

AJ won a battle royal on April 22, 2013, to become the number one contender to Kaitlyn’s WWE Divas Championship. Kaitlyn soon began a storyline where she received gifts from a secret admirer. On June 10, after setting up Langston to pose as the admirer, AJ revealed it to be a mind game, berated Kaitlyn and left her in tears. Six days later at Payback, AJ defeated Kaitlyn to capture her first Divas Championship. While she continued to mock Kaitlyn, they participated in the first ever in-ring contract signing for a Divas Championship bout. At Money in the Bank on July 14, AJ won their rematch but later in the show caused Ziggler to lose his own rematch for the World Heavyweight Championship. She hit his opponent, Alberto Del Rio, with her title belt to protect him from further head injury, prompting a disqualification. Angered by her unwanted action, Ziggler ended their relationship. She exacted revenge by costing him another match, then attacked him with Langston. On August 2, Langston was banned from attending her matches. However, AJ again retained the title from Kaitlyn, who was betrayed by Layla. Kaitlyn and Ziggler ultimately joined together to defeat AJ and Langston in a mixed tag team match at SummerSlam on August 18.

In January 2014, AJ became the longest-reigning Divas Champion at the time. After fending off title contenders Cameron and Natalya, AJ renewed her on-screen rivalry with SmackDown General Manager Vickie Guerrero, who forced her to defend the Divas Championship in a 14-woman match at WrestleMania XXX. AJ won the match on April 6, marking the first time the championship had been contested for at WWE’s flagship event. The next night on Raw, AJ challenged the debuting Paige to an impromptu title match and was defeated, ending her then-record reign at 295 days. Mendez was subsequently granted time off.

AJ returned on the March 2 episode of Raw, saving her former rival Paige from an attack by Nikki and Brie Bella. AJ and Paige allied together to defeat the Bella Twins at WrestleMania 31 on March 29. A six-woman tag team match the next night on Raw wound up being her final match, as WWE announced her retirement from in-ring competition on April 3. In her memoir, Mendez stated that permanent damage to her cervical spine, and the fulfillment of her goals led to the decision. She had also “felt caught in the middle” between WWE and her husband Phil Brooks following his controversial departure in January 2014 but continued to wrestle for as long as she could.

Mendez married fellow wrestler Phil Brooks, better known as CM Punk, on June 13, 2014. They reside in Chicago.

In February 2015, Mendez criticized WWE’s treatment of its female wrestlers, stating they receive only a fraction of the wages and screen time of their male counterparts despite having generated record-selling merchandise and several top-rated segments. Her comments addressed WWE executive Stephanie McMahon, who thanked her for the public statement. WWE chairman and CEO Vince McMahon acknowledged the issue.

Mendez wrote Crazy Is My Superpower: How I Triumphed by Breaking Bones, Breaking Hearts, and Breaking the Rules, a memoir published by Crown Archetype on April 4, 2017. The book covers her upbringing and career in professional wrestling. It debuted at No. 10 on The New York Times Best Seller list for hardcover non-fiction. Upon release, she described writing as “very much the next chapter” of her life, and had begun work on a second book. In collaboration with actress Aimee Garcia, Mendez co-wrote the comic book series GLOW vs. The Babyface, based on the television series GLOW; the first of four issues was published by IDW Publishing in November 2019. Mendez and Garcia reunited to write the Dungeons & Dragons comic series At the Spine of the World; its first issue will be published by IDW in October 2020.