The new mobile OS, which features Facebook integration, Apple's own Maps system and improvements to Siri, will become available to download at 10am Pacific Time and 1pm Eastern time, which is 6pm BST.
A full timetable of the rollout times worldwide has been posted on Twitter.
iOS 6 can be downloaded for free for iPhone 3GS, iPhone 4, iPhone 4S, the new iPad, iPad 2 and iPod touch (fourth generation upwards), although some of its features are not available for all products.
For the first time, the update will be available over-the-air, meaning that you won't have to plug in your device to download and install the software, as long as you are already on iOS 5.
However, it is advisable to back up your device before downloading the new software, after problems reported by some users of the wiping of their apps and images following the launch of iOS 5 last year.
As with past iOS rollouts, there could also be long waits for some people, as Apple is generally hit by heavy download traffic when it pushes out software updates due to its massive worldwide iDevice user base.
Apple's iPhone 5, the firm's latest smartphone featuring a four-inch screen, faster A6 processor, improved camera and new dock connector, will ship with iOS 6 when it officially launches on Friday (September 21). The same is true for the fifth generation of the iPod Touch.