The Simpsons is now in its 17th series on US television
The movie will be released in the United States in July 2007.
A 25-second trailer for the film has been shown to US audiences at screenings of Ice Age: The Meltdown, promising to introduce "the greatest hero in American history".
It then cut to Homer Simpson, wearing only his underwear, who admitted: "I forgot what I was supposed to say."
The Simpsons revolves around the antics of bald, beer-guzzling family man Homer and his spiky-haired son Bart.
It is the longest-running prime-time entertainment series on television in the US and a worldwide hit.
It is currently in its 17th season, and last month, US network Fox confirmed it had commissioned two more series.
This ensured the show would stay on screens until at least 2008.
There has long been speculation about whether it would be turned into a film.
Creator Matt Groening said last year that the animated hit would keep going as long as he and his colleagues could keep generating fresh ideas."That's what you're looking for in television - surprise," he added.