The new console features processor chips and graphical power normally associated with high-end gaming PCs, which can cost several thousand pounds.
Xbox boss Phil Spencer said the company's aim is to "delight gamers", and also confirmed the One X will support backwards compatibility - enabling gamers to play games originally intended for the older Xbox One console.
The new Xbox will go on sale on November 7, it was confirmed, and it has the ability to show games in "true 4K" not seen before, the firm says.
It will also have the power to improve picture quality on televisions without 4K capability, as well as shorten loading times on older games.
A host of new games were unveiled alongside the new console, including a new instalment in the Assassin's Creed series - which last year was made into a movie starring Michael Fassbender.
When first announced last year under the codename Project Scorpio, it was suggested the increased specifications of the One X were to enable the device to support virtual reality headsets.
Sony took such an approach with the PS4 Pro, marketing it as the best companion for its PlayStation VR headset, which has sold a million units since launch last year.
However, Microsoft did not announce a single virtual reality game during its press conference, which took place ahead of the opening of video games convention E3 in Los Angeles on Tuesday.
The "niche" nature of virtual reality was the reason for this, Mr Harding-Rolls claimed.
"While the One X has the power to drive VR experiences, Microsoft's lack of VR coverage at its press event underlines that VR remains a niche pursuit and that it will not be rolling out headset support until at least 2018," he said.
PlayStation will hold its own preview event on Monday night, where it is expected to reveal a line-up of high-profile games, including the new Call Of Duty and a sequel to Bafta award-winning survival game The Last Of Us.
Additional reporting by Press Association
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