Apple has sold more than 1.2 billion iPhones over the past decade and ushered in the era of mobile computing, but last year had a substantial decline in revenue as many consumers rejected the iPhone 7 as being too similar to the iPhone 6.
The screen on the iPhone X is about the size of the current iPhone 7 plus, though the phone itself is smaller.
It features richer colours courtesy of a new technology called OLED that other vendors such as Samsung are also rolling out.
The company also introduced an upgraded Apple Watch, which can make phone calls and access the internet without the user carrying an iPhone.
Mr Cook announced the launch at the Steve Jobs Auditorium at Apple's new campus — never before opened to the public — with a tribute to co-founder and former CEO Jobs, who died in 2011.
The Apple building itself was considered to be Jobs' final product, and Mr Cook spent a few minutes boasting about the design, energy-saving features and public spaces at the new campus, including a flagship Apple Store.
The iPhone 8 and 8 Plus cost $1,079 and $1,229 respectively, whereas the X will start at $1,579.
The iPhone X, however, will be available from November 3, whereas the iPhone 8 will be released on September 22.
iPhone X and 8 launched
