Bosses of the HBO show made the revelation via social media, in an elaborate live video stunt.
Fans watched for more than an hour in anticipation as a huge block of ice in a room lit with torches melted away to reveal the date they had been waiting for.
The video then continued with teaser clips of the upcoming series, complete with a fresh wave of battles, dragons and creepy creatures.
In a new trailer, returning character Jon Snow says: "There is only one war that matters. The Great War. And it is here."
After being pushed back from its usual April launch, this will mark the show's penultimate series.
It will be available from 2am on Sky Atlantic on July 17 and online streaming service Now TV, followed by a repeat at 9pm the same day.
The sixth season culminated in Daenerys setting sail for the Seven Kingdoms, Snow dubbed King of the North, Cersei seizing the Iron Throne and the Night King amassing forces.
According to broadcasters, the coming series promises a "brutal, bloody and wintry return to Westeros".
Due to the time difference, the series' official launch date in the USA is July 16.