Which John Ford film gave him his first Best Director Oscar?

The John Ford film that gave him his first Best Director Oscar was The Informer.

Released in 1935, The Informer is a stark drama set in Dublin during the Irish War of Independence. Ford directed Victor McLaglen as Gypo Nolan, an impoverished former Irish Republican Army member whose betrayal of a friend leads to guilt, paranoia, and tragedy. McLaglen won the Academy Award for Best Actor, while Ford won Best Director.

The award was presented at the 8th Academy Awards, honoring films released in 1935. Ford later won the same directing prize for The Grapes of Wrath, How Green Was My Valley, and The Quiet Man. Those victories helped make him the record holder for most Best Director Oscars.

A common mix-up is Stagecoach, one of Ford's most influential films and a Best Director nominee, but it did not bring him his first directing Oscar. The Informer was the first of Ford's four competitive Best Director wins.