Joey Lynn King was born on 30 July 1999 in Los Angeles to Jamie King, of Jewish descent, while her father, Terry, a former arm-wrestling champion, worked as a consultant for Sylvester Stallone. During her early years, Joey King attended the Phoenix Ranch School in Simi Valley, California. But as she began acting professionally at the age of four, her formal primary and secondary education was completed through home-schooling to accommodate her demanding filming schedules, and she never attended a traditional college. Possibly, she inherited her love of acting from her grandmother, who used to perform in live theatre, and made her first forays into acting as a toddler in local community theatre productions and then, landed her first professional job in a commercial for Life cereal at age four.

After more than a hundred commercial appearances and roles in a number of television series, along with a short film Grace in 2006, Joey King landed the breakout role of the imaginative Ramona Quimby, whose character always seems to be in some trouble, co-starring with Selena Gomez, playing the role of her caring big sister Beezus, in Ramona and Beezus (2010), for which she won a Young Artist Award, followed by the role of Kirsten, a terrified young girl rescued and protected by the United States Marine Corps platoon, in the alien invasion science Fiction film Battle: Los Angeles (aka World Invasion 2011). The same year, she also appeared as Molly Weaver, the younger sister of Emma Stone’s character, in the romantic comedy film Crazy, Stupid, Love (2011). Joey King demonstrated her commitment to her dedication when she shaved her head for her small but important role of Talia Al Ghul in The Dark Knight Rises (2012), the third Batman film directed by Christopher Nolan, one of her first major blockbuster films, at the climax of which the young Talia was shown climbing out of the prison pit.

The next year, Joey appeared in the fantasy film Oz the Great and Powerful (2013), directed by Sam Raimi, portraying the role of a sweet, wheelchair-bound, unnamed girl who attends Oscar's magic show and desperately asks him to heal her legs. Apart from that, she also lent her voice in the film, for an orphaned, living china doll whose village is destroyed by Evanora, the power-hungry ruler of the Emerald City. In the same year, she appeared and played significant roles in three more films, which include Roland Emmerich's White House Down (2013), playing the role of Emily Cale, the daughter of a police officer who gets caught in the White House after terrorists take over in an attempt to assassinate the United States president. Joey earned outstanding reviews for her performance in the film from eminent film critics such as Roger Ebert of the Chicago Sun Times and Amy Biancolli of the San Francisco Chronicle.

In the same year, apart from the comedy film Family Weekend (2013), in which she appeared as Lucinda Smith-Dungy, a quirky 9-year-old girl who frequently dresses up and acts like characters from restricted films, Joey also appeared in the critically acclaimed horror film, The Conjuring (2013), in which she played the role of Christine, one of the five Perron daughters, whose mother gets possessed by a demon and her stunning performance in the film, with terror in her wide-eyes, particularly in one notable sequence in which she was haunted by an unseen demon standing in the shadows behind a door, telling her that it wants her family dead, was widely acclaimed by the critics.

Joey King shaved her head for the second time in her career for playing the role of Grace Bloom, the daughter of Aidan, played by Zach Braff, a struggling actor who home-schools his kids and finds adventure along the way, in the comedy-drama film Wish I Was Here (2014). Her other important roles during the decade, apart from the roles in several television serials like Fargo (2014-2025), Tween Fest (2016) and The Flash (2016), include the lead role of Clare Shannon in the horror-thriller film Wish Upon (2017), the role of the 16-year-old Jamie Winkle in the coming-of-age film Summer ’03 (2018), and the role of Wren in the paranormal horror film Slender Man (2018). However, her profile gained a significant boost from her starring role in the romantic comedy film The Kissing Booth (2018), along with its sequels The Kissing Booth 2 (2020), and The Kissing Booth 3 (2021).

However, Joey perhaps reached the peak of her career when she appeared in the profusely acclaimed series The Act (2019), playing the real-life Munchausen syndrome by Proxy victim Gypsy Rose Blanchard, for which she had to shave her for the third time in her career. Throughout her childhood and adolescence, Gypsy was subjected to extensive medical trauma by her mother, who forced her to use a feeding tube, carry an oxygen tank, and undergo multiple unneeded surgeries, including the removal of her salivary glands. She claimed that Gypsy suffered from numerous physical disorders which include leukaemia, muscular dystrophy, epilepsy, and chromosomal defects. In addition, she isolated her from peers, physically abused her, and forced her to act as though she had a developmental delay, only to gain financial and public sympathy. Finding no other way to escape from the unusual trap, Gypsy conspired with her online boyfriend, Nicholas Godejohn, who travelled to her home in Springfield, Missouri, and fatally stabbed the mother, Clauddine "Dee Dee" Blanchard, on 14 June 2015, while Gypsy was in another room. Both Gypsy and Godejohn fled to Wisconsin, but were quickly apprehended, and in 2018, Godejohn was convicted of first-degree murder and sentenced to life in prison, while pleading guilty to a lesser charge of second-degree murder, Gypsy was sentenced to 10 years, and was subsequently released from the Chillicothe Correctional Center in Missouri in December 2023. For her wonderful performance in the role of Gypsy, Joey King was nominated for a 2020 Golden Globe Award, and was earned nomination for an Emmy Award in 2019.

In her personal life, Joey King has two older sisters, Hunter King and Kelli King, both of whom are also actresses. She had one highly publicised relationship with Jacob Elordi, whom she met while filming The Kissing Booth. They became one of Hollywood's most prominent young couples, dated for over a year, but ultimately broke up in late 2018. Later, she met director and producer Steven Piet in 2019, while filming the famous series The Act. The couple became engaged in February 2022 and tied the knot on 2 September 2023, during an intimate ceremony in Mallorca, Spain.