Landing at a 100 percent Fresh rating out of a total of 177 reviews, USA Today reports that the film has knocked the previous placeholder, Toy Story 2, out of the top slot.
Lady Bird marks the directorial debut of actress Greta Gerwig, who has starred in many Rotten Tomatoes Certified Fresh films, such as Frances Ha, The House of the Devil, Jackie and Greenberg, her breakout role opposite Ben Stiller.
The site's "critics consensus" reveals that the overwhelming majority of reviewers feel that the film "delivers fresh insights about the turmoil of adolescence — and reveals writer-director Greta Gerwig as a fully formed filmmaking talent."
"We put our heart and souls into this movie, and the last step of this deeply collaborative art form of filmmaking is giving the film to the audience and the film critics," she added. "That there has been such a warm reception is a dream come true."
The film stars Saoirse Ronan (The Grand Budapest Hotel) as Christine "Lady Bird" McPherson, an teenage girl who "fights against but is exactly like her wildly loving, deeply opinionated and strong-willed" mother, played by Roseanne's Laurie Metcalf.
Lady Bird is now playing in theaters nationwide.