The iPhone X (Roman numeral "X" pronounced "ten") is a smartphone designed, developed, and marketed by Apple Inc. It is the eleventh generation of the iPhone. It was available to pre-order on October 27, 2017 and was released on November 3, 2017.

The iPhone X was intended to showcase what Apple considered the technology of the future. Using a glass and stainless-steel form factor and "bezel-less" design, shrinking the bezels, and not having a "chin", unlike many Android phones. It was the first iPhone to use an OLED screen. The home button's fingerprint sensor was replaced with a new type of authentication called Face ID, which used sensors to scan the user's face to unlock the device. This face-recognition capability also enabled emojis to be animated following the user's expression (Animoji). With a bezel-less design, iPhone user interaction changed significantly, using gestures to navigate the operating system rather than the home button used in all previous iPhones. At the time of its November 2017 launch, its price tag of $999 USD also made it the most expensive iPhone ever, with even higher prices internationally due to additional local sales and import taxes.

The iPhone X received positive reviews. Its display and build quality were universally praised, and the camera also scored positively on tests. However, the sensor housing "notch" at the top of the screen and the introduction of an all-new authentication method were polarizing for critics and consumers. The notch was heavily mocked by users on social media, although app developers responded either neutrally or positively to the changes it brought to the user experience in their apps and games. Face ID facial recognition was praised for its simple setup, but criticized for requiring direct eyes on the screen, though that option can be disabled within the system preferences.

Along with the iPhone 6s, its Plus variant, and the first-generation iPhone SE, the iPhone X was discontinued on September 12, 2018 following the announcement of the iPhone XS, iPhone XS Max and iPhone XR devices. As a result, with a shelf life of just over 10 months, the iPhone X had the shortest ever tenure as the flagship device in the history of the iPhone.

On November 22, 2018, Apple reportedly resumed production of the iPhone X due to weak sales of its successors. The iPhone X remains discontinued, but as of February 2019, Apple started selling refurbished models starting at $769. In November 2019, Apple reduced the price to $599/£699.