Meghann Fahy was born on April 25, 1990 in Longmeadow, Massachusetts, USA. She first appeared on ABC's One Life to Live in February 2010 as college student Hannah O'Connor. The role ended in November 2010, with Fahy appearing as Hannah in two subsequent episodes in January 2012. Other television credits include a guest appearance on the series Gossip Girl as Devyn. In 2011, Fahy appeared in the Hallmark Hall of Fame film The Lost Valentine as a young 1940s-era mother, Caroline Thomas, with Betty White as Caroline in present-day and Jennifer Love Hewitt as a reporter learning of Caroline's story. The following year, Fahy appeared in the miniseries Political Animals as ambitious blogger Georgia, and guest starred on Necessary Roughness as Olivia DiFlorio, tutor-turned-girlfriend of the main character's son.

In 2016, Fahy was cast as Sutton Brady in the Freeform drama series The Bold Type, which premiered on June 20, 2017. She has won praise for her performance in this role, with one reviewer noting that "Fahy, giving one of TV's most charming and underrated performances, continues to define the show's fizzy, occasionally bawdy comic streak with exquisite timing and a particular aptitude for punchlines that hurt just a little bit". In November 2020, she was cast in a co-starring role in the drama film The Unbreakable Boy. She will be portraying the role of Teresa LeRette, mother to Austin.

In February 2022, Fahy was cast in a starring role playing Daphne Sullivan, a woman vacationing with her husband, in the second season of the HBO drama anthology series The White Lotus. Her performance was praised, with Vanity Fair proclaiming that Fahy would be the "breakout" star of the series' second season. Along with her castmates, Fahy garnered an SAG Award for Outstanding Performance by an Ensemble in a Drama Series. She also received a nomination for Outstanding Supporting Actress in a Drama Series at the 75th Primetime Emmy Awards for her performance.