Ronan made her acting debut with the Irish medical drama series The Clinic in 2003 and her first film appearance was in a supporting role in the romantic comedy I Could Never Be Your Woman in 2007. Her breakthrough came with the part of a precocious teenager in Atonement (2007), for which she was nominated for the Academy Award for Best Supporting Actress. Ronan followed this with starring roles of a murdered girl seeking closure in The Lovely Bones (2009) and a teenaged assassin in Hanna (2011), and the supporting part of a baker in The Grand Budapest Hotel (2014). She received critical acclaim for playing a homesick Irish girl in 1950s New York in the romantic drama Brooklyn (2015) and the titular role of a high school senior in Greta Gerwig's coming-of-age film Lady Bird (2017). She won the Golden Globe Award for Best Actress for the latter and earned nominations for the Academy Award for Best Actress for both films.