The Apple Pencil and Apple's new Smart Keyboard will also be available to order on Wednesday.
In a statement announcing the release, Apple's senior vice president of worldwide marketing Phil Schiller said: 'The early response to iPad Pro from app developers and our customers has been incredible, and we're excited to get iPad Pro into the hands of customers around the world this
'iPad Pro is the most powerful iPad we've ever made, giving users the ability to be even more creative and more productive.'
The iPad Pro has a 12.9-inch Retina display with 5.6 million pixels, giving it a resolution of 2732 x 2048 at 264 pixels per inch (PPI). It also has a fingerprint-resistant coating.
It is powered by a 64-bit A9X chip, has a 10-hour battery life and weighs 1.5lbs (713g).
Rumours about the larger iPad started circulating last year and Apple finally revealed the device in September.
Apple Pencil will be available for £79 ($99 in the US) and Smart Keyboard will be available in charcoal grey for £139 ($169 in the US).