'The Day of the Doctor', starring Matt Smith and David Tennant, is to be simulcast on November 23 this year.
The feature-length episode will be shown in at least 75 countries around the world at the same time, including Brazil, Canada, USA, Australia and Mexico.
Meanwhile, cinemas in the UK are to screen the 75-minute episode in 3D - details of which are to be announced shortly.
Speaking about the simulcast, showrunner Steven Moffat said: "The Doctor has always been a time traveller - now he's travelling time zones. On the 23rd of November, it won't be the bad guys conquering the Earth - everywhere it will be 'The Day of the Doctor'!"
Last Saturday (September 28), two teaser trailers for the special aired on BBC One.
The brief teasers - which aired before and after the opening episode of Atlantis - revealed the official hashtag of the celebratory episode to be #SaveTheDay.
Doctor Who: The Doctors in pictures