The 400 Blows (French: Les quatre cents coups) is a 1959 French coming-of-age drama film, and the directorial debut of François Truffaut, who also co-wrote the film. Shot in the anamorphic format DyaliScope, the film stars Jean-Pierre Léaud, Albert Rémy, and Claire Maurier. One of the defining films of the French New Wave, it displays many of the characteristic traits of the movement. Written by Truffaut and Marcel Moussy, the film is about Antoine Doinel (a semi-autobiographical character), a misunderstood adolescent in Paris, who struggles with his parents and teachers due to his rebellious behavior. It was filmed on location, in Paris and Honfleur.

The 400 Blows received numerous awards and nominations, including the Cannes Film Festival Award for Best Director, the OCIC Award, and a Palme d'Or nomination in 1959, and was also nominated for an Academy Award for Best Original Screenplay in 1960. The film had 4.1 million admissions in France, making it Truffaut's most successful film in his home country.

The 400 Blows is widely considered one of the best films ever made; in the 2022 Sight & Sound critics' poll of the greatest films ever made, it was ranked 50th. It ranked 33rd in the directors' poll on the same list.

It is the first in a series of five films in which Léaud plays the lead character. The film is followed by a short film, Antoine and Colette (1962) and three legacy sequels, Stolen Kisses (1968), Bed and Board (1970) and Love on the Run (1979), with the actor reprising his role as Doinel.