Elgort was born in Manhattan. His parents are Arthur Elgort, a fashion photographer who has worked extensively for Vogue for over thirty years, and Grethe Barrett Holby, an opera director. His father is of Russian Jewish descent, and his mother is of Norwegian, English, and German ancestry. His maternal grandmother, Aase-Grethe, was in the Norwegian resistance during World War II, and saved Norwegian Jewish children by moving them into neutral Sweden; because of these activities, she was imprisoned in a concentration camp. Elgort is named after photographer Ansel Adams.
Elgort has two older siblings, Warren, a film editor, and Sophie, a photographer. At the age of nine, his mother took him to try out for School of American Ballet. He attended The Professional Performing Arts School, Fiorello H. LaGuardia High School and Stagedoor Manor summer camp. Elgort started taking acting classes at the age of twelve and at LaGuardia, Elgort performed in a rendition of Hairspray with Kyle Jean-Baptiste and starred in his school's productions of Guys and Dolls.
Elgort's acting career began through professional stage acting, in Regrets, by Matt Charman. His film debut was a secondary role in the 2013 remake of Carrie. His first highly publicized role was in Divergent as Caleb Prior, the brother of Beatrice Prior (played by Shailene Woodley). The film, based on a popular young adult novel by Veronica Roth, was released on March 21, 2014.
Immediately after the filming of Divergent was completed, it was announced that Elgort would play Augustus Waters in the film adaptation of John Green's novel The Fault in Our Stars, opposite Woodley who would play Hazel Grace Lancaster. The film followed the story of Hazel, a teenage cancer patient, who is forced by her parents to attend a support group, where she subsequently meets and falls in love with Waters, an ex-basketball player. The film, directed by Josh Boone, was released on June 6, 2014. Elgort next co-starred in the comedy film Men, Women & Children, directed by Jason Reitman and released in October 2014.
In 2014, Elgort was named one of the best actors under twenty years of age. Elgort reunited with Chloe Grace Moretz to present the award for Best Visual Effects at the 2015 Oscars. He also reprised his role, Caleb Prior, in The Divergent Series: Insurgent, the second film of the book series Divergent, which was released March 20, 2015, and in the third film, The Divergent Series: Allegiant, which was released on March 18, 2016.
Elgort was on a shortlist of actors being considered to play the role of Han Solo in a still-untitled 2018 Han Solo film; Alden Ehrenreich was eventually cast in May 2016. Elgort expressed some relief at not being cast, saying that, if he had been cast, he would have had to change his DJ name, Ansølo.
In 2017, Elgort played the title role in the action film Baby Driver, directed by Edgar Wright, and also starring Lily James and Kevin Spacey. The film received positive reviews and performed well at the box office. Throughout much of the film, Elgort wears a jacket that some thought was deliberately meant to look like the jacket worn by Han Solo in the original Star Wars films, as a node to Elgort's then-potential casting, though Wright insisted that the resemblance was unintentional.
Elgort will play Addison Schacht in the adaptation of The November Criminals, with Chloë Grace Moretz, and will star in the film Billionaire Boys Club, opposite Kevin Spacey, Carey Elwes, Emma Roberts and Taron Egerton, and directed by James Cox. Both films are in post-production.
On June 23, 2014, Deadline.com announced that he had been cast in the titular role in Van Cliburn. Based on the biography by Howard Reich, the film will depict Van Cliburn's rise to fame in 1958 when, in the midst of the Cold War, Cliburn won the first International Tchaikovsky Competition in piano - an extraordinary event, since Cliburn was from the US. The adaptation will be produced by Wyck Godfrey and Marty Bowen, who also produced The Fault in our Stars. On June 27, 2017, it was announced that Elgort would portray future President John F. Kennedy during his time in the United States Navy in the film Mayday 109.
He is represented by CAA and Brookside Artist Management's Emily Gerson Saines.
Under the name Ansølo, Elgort created a SoundCloud account to publish electronic dance music, and he has remixed songs such as "Born to Die" by Lana del Rey. In a livestream in February 2014 he stated he had signed a record deal with Tom Staar's new label Staar Traxx and Steve Angello Size Records.
His first record "Unite" was released on April 21, 2014, on Beatport, and May 5, 2014, on iTunes. His second record, "Totem", was released July 21, 2014, on Beatport and iTunes. His single "To Life", a Bar Mitzvah-themed song inflected with klezmer music, was released in September 2015.
He played at the Electric Zoo Festival main stage in 2014, the Ultra Music Festival main stage in March 2015, played in a red-light dance music event in Amsterdam in 2014, opened some The Chainsmokers shows, a NERVO show, and some others shows with his friends Nicky Romero and Martin Garrix. He played his first headline show on his 21st birthday on Pacha NYC.
In 2015, he signed a record deal with Island/Universal Records, and released his first single titled "Home Alone" in July 2016.
On February 3, 2017, he released a single called "Thief" under the name Ansel Elgort. The music video featured his girlfriend Violetta Komyshan, a ballet dancer.
He was featured on rapper Logic's third studio album, Everybody, released on May 5, 2017, on a song titled "Killing Spree".
Elgort began dating his high school sweetheart, Violetta Komyshan, in 2012. The couple broke up in August 2014 primarily due to the actor's burgeoning career and hectic schedule but reconciled after five months of separation in January 2015.
He is a skateboarder and an avid sportsman, often seen playing pickup basketball. As a hobby, he also took to miniature painting displaying some of his work. He has eight million followers on Instagram.