Rachel Zegler was born in Hackensack, New Jersey, in 2001 to Gina and Craig Zegler. She was named after the fictional character Rachel Green from the TV series Friends. She has an older sister named Jacklyn. Her mother is of Colombian descent. Her maternal grandmother immigrated from Barranquilla, Colombia to the United States in the 1960s. Her father is of Polish descent.

She was raised in Clifton, New Jersey, where she attended St. Philip the Apostle Preparatory School. Afterwards, she attended the Catholic all-girls college-preparatory Immaculate Conception High School, which she graduated from in 2019.

Zegler began her career starring in several musicals while in high school, playing Belle in Beauty and the Beast (2016), Ariel in The Little Mermaid (2017), Dorothy Brock in 42nd Street (2018), and Princess Fiona in Shrek The Musical (2019). For all four performances, she received Metro Award nominations in the Actress in a Leading Role category. Her other roles have includes Serena in Legally Blonde, Cosette in Les Misérables, and Millie in Thoroughly Modern Millie. Her YouTube channel has been active since July 2015 which garnered media coverage and positive critical reception. As of 2022, her video of herself singing « Shallow », from A Star Is Born, had garnered over 12.2 million views on Twitter.

In January 2018, director Steven Spielberg posted an open casting call via Twitter for a new film adaptation of West Side Story. Zegler, then 16 years old, responded to the casting call tweets with videos of herself singing « Tonight » and « I Feel Pretty »; she had performed the role at the Bergen Performing Arts Center in 2017. She was selected from over 30,000 applicants for the role of Maria, marking her film debut. The film was released in December 2021, and earned acclaim from critics and audiences. For her performance, she received a Critics’ Choice Movie Award nomination for Best Young Performer and won the Golden Globe Award for Best Actress – Motion Picture Comedy or Musical, making her the first actress of Colombian descent to win in that category as well as the youngest winner in that category at 20 years old.

She starred as Anthea in the superhero film Shazam! Fury of the Gods (2023). The film received mixed reviews. She played protagonist Lucy Gray Baird in the 2023 film adaptation of the Hunger Games prequel The Hunger Games: The Ballad of Songbirds & Snakes. The film received positive reviews. David Ehlrich of IndieWire praised Zegler wrtiting, « [She] is absolutely captivating in a Wild Rose-coded performance that’s equal part Southern pluck and wide-eyed terror…it is a marvel of multiplex acting ». Ehlrich also noted the nuances of her performance adding « Zegler knows how to play nuance big enough for the back of the room to read it all over her face ». She next appeared in Kyle Mooney’s directorial debut film Y2K, produced by A24, which debuted at the South by Southwest Festival in 2024.

She will voice the lead character in the animated musical film Spellbound, directed by Vicky Jenson, which is scheduled to be released in 2024 and will premiere on Netflix. She has been cast as the titular character in Snow White, a live-action adaptation the 1937 animated Disney film, scheduled to be released in March 2025. Zegler is also set to make her Broadway debut playing Juliet in a musical adaptation of William Shakespeare’s Romeo & Juliet directed by Sam Gold with music by Jack Antonoff later in 2024.

In February 2021, Zegler and actor Josh Andrés Rivera confirmed that they were dating. The two had met on the set of West Side Story.