Oliver Martyn John Phelps was born on February 25, 1986, in Sutton Coldfield, Birmingham, England, thirteen minutes before his twin brother James. He and James skipped school in 2000 to audition for the Harry Potter films, where he was cast as George Weasley. Like his twin brother, he received on-set tutoring throughout the decade-long production of the franchise.

Oliver portrayed George Weasley across all eight Harry Potter films from 2001 to 2011. He also reprised his role in the 2022 HBO Max special Harry Potter 20th Anniversary: Return to Hogwarts. Like his brother, he remains deeply tied to the Wizarding World, participating in major franchise events, including the 2025 opening of Universal Epic Universe at Universal Orlando Resort in Florida.

Beyond acting, Oliver co-created the Normal Not Normal podcast with James, where they interview celebrities about fame and personal growth. In 2024, the twins debuted as co-hosts of Harry Potter: Wizards of Baking on Food Network. Oliver is also an avid golfer, and he notably completed the 2025 New York City Marathon in November, raising funds for the Matt Hampson Foundation.