Greta Gerwig has scored a critical hit with her directorial debut Lady Bird.

The coming-of-age film has earned a 100 per cent fresh rating on review aggregation site Rotten Tomatoes, making it now the best reviewed movie on the site - beating Toy Story 2.

Speaking to Vanity Fair, Greta shared her surprise and delight at the film’s critical reception, admitting that at first she didn’t believe it.

Greta GerwigGreta Gerwig is thrilled at the critical response to Lady Bird

“It’s amazing,” she told the magazine at the Gotham Awards red carpet on Monday night.

Greta revealed that it was her younger brother who first told her that Lady Bird had overtaken Toy Story 2 as the site’s best reviewed movie - meaning she was“also slightly skeptical” at the news.

“It’s so exciting,” she continued. “You make a movie and you put so much into it . . . to have it reflected back to you, it’s an amazing thing.”

More: Greta Gerwig To Make Solo Directorial Debut With Lady Bird

At Monday night’s Gotham Awards, star Saoirse Ronan picked up a best-actress award- surely the first of many more to come once awards season gets in full swing.

Lady Bird, which was also written by Greta, tells the story of Christine 'Lady Bird' McPherson, a rebellious Catholic school girl during her senior year of high school.

Saoirse stars as the title character, with Laurie Metcalf as her equally strong-willed mother, who she frequently clashes with.

The film has already earned $11 million at the box office and is up for four Independent Spirit Awards.