Lucas has kept fans guessing
Lucas announced on his official Star Wars website on Monday that the film would be called Star Wars: Episode II - Attack of the Clones.
The film is due to be ready for cinema release in the US in early 2002 but, until now, Lucas has kept its title a closely guarded secret.
Attack of the Clones follows previous films A New Hope, The Empire Strikes Back, Return of the Jedi and The Phantom Menace.
For Star Wars fans, waiting to hear the name given to the next film in the globally popular series had become something of a game.
Lucas acknowledged this anticipation when making his announcement on the Star Wars website.
He described the name Attack of the Clones, saying: "It harkens back to the sense of pure fun, imagination and excitement that characterised the classic movie serials and pulp space fantasy adventures that inspired the Star Wars saga."
Plot
Lucas also summarised the film's plot. The action will take place 10 years after that in The Phantom Menace.
British actor Ewan McGregor, one of the stars of The Phantom Menace, will return as the Jedi knight Obi-Wan Kenobi. The role was originally played by the late Sir Alec Guinness in Lucas' first three films.
And Natalie Portman will also resume her role as Padme Amidala. Hayden Christensen will be joining the cast to play the young adult Anakin Skywalker.
The film will follow Obi-Wan Kenobi and Anakin Skywalker as they are assigned to protect Padme Amidala when her life is threatened by a faction of political separatists.
Fans
Speculation over the title of the fifth Star Wars has been running high among fans on the internet.
Having set up their own tribute sites devoted to Star Wars, fans have published what they thought to be possible titles, including The Shadow Falls.
Star Wars has one of the largest internet fan bases for a movie franchise.
This enthusiasm for the movies led to The Phantom Menace alone netting Lucas a $400m (£253.4m) fortune.
Lucas's movie career began at the prestigious University of Southern California film school.
In total the writer and director has picked up 17 Academy Awards and 66 nominations and six Bafta awards for his Star Wars movies and other films such as the acclaimed American Graffiti.