The new console contains the fastest processor chip ever used in a games console, Xbox said, and will offer "true" 4K gaming to users.
The One X will go on sale on November 7, Microsoft confirmed during a showcase ahead of E3, one of the gaming industry's largest conventions.
The console, originally known as Project Scorpio, is set to rival Sony's PlayStation 4 Pro - which launched last year - as the flagship games console on the market.
Microsoft has been under pressure to overtake Sony, after the current generation PS4 steadily outsold the Xbox One following the launch of the two systems in 2013.
Xbox boss Phil Spencer said the new system would also feature the "most diverse" line-up of games ever produced by the firm.
During a press conference, some of the first off these games were previewed, including a new game from the popular Assassin's Creed franchise - Origins.
Microsoft also demonstrated a new game in its exclusive racing series, Forza Motorsport 7.
The E3 show floor opens in Los Angeles on Tuesday.
Mr Spencer confirmed the Xbox One X will cost £449 when it goes on sale on November 7.
The Xbox boss also announced that the console's backward compatibility scheme - which enables old games from previous consoles to be played on the newest systems - was being extended to the original Xbox.
Mr Spencer said video games should be "celebrated" in the same way as books and films.
"Xbox empowers game developers, large and small, to create different types of games for every type of player," he said.
"Not only do we have the biggest cross-platform blockbusters on our platform, we've also scoured the world to bring our fans unique content from creative artists that capture the imagination."
Fellow gaming giants Nintendo and Sony are among those who are also due to unveil a host of new games during E3, while the next game in the Call Of Duty series is also expected to be demoed for the first time.