Samurai is correct, but the Jazz Singer only had about a quarter of the film with speaking. The first full length film to feature dialogue throughout was Warner Bros.' 1928 gangster flick, Lights of New York.
The first feature length film made it's way to the big screen in October of 1927. 'The Jazz Singer' told the story of young Jackie Robonowitz who, now wanting to follow his fathers' dreams for him to become a Cantor for his synagogue ran away from home at the tender age of thirteen. Away from his fathers' desires and influence, Jackie Robonowitz was able to work on his own dream of becoming a jazz singer. Working in a small caf Jackie meets Mary Dale who, impressed by his singing ability, finds Jakie a job. The newly discovered Jackie Robonowitz becomes known as Jack Robin the jazz singer. After being disowned by his father in his early teenage years, Jackie returns to be with him as he lies in his deathbed. Jackie's father is willing to forgive his son if he will only sing as Cantor. Choosing family and forgiveness over his own musical future, Jackie grants his father his hearts desire. Appropriately, the leading actors first line was, 'You ain't heard nothing yet.'