Android "Oreo" (codenamed Android O during development) is the eighth major version of the Android mobile operating system. It was first released as an alpha quality developer preview on March 21, 2017. The second developer preview was released on May 17, 2017, and it is considered beta quality and the third developer preview was released on June 8, 2017 and finalizes the API. On July 24, 2017, a fourth developer preview was released which includes the final system behaviors and the latest bug fixes and optimizations. It was released to the public on August 21, 2017.

Google unveiled a statue of the dessert-themed update at 14th Street Park in Manhattan, close to the original Nabisco factory that created the first Oreo.

On March 21, 2017, Google released the first developer preview of Android "O",  available for the Nexus 5X,  Nexus 6P,  Nexus Player,  Pixel C, and both Pixel smartphones. The second, considered beta quality, was released May 17, 2017.The third DP was released on June 8, 2017. The fourth and final beta release was released on July 24, 2017.

DP3 finalized the release's API to API level 26, changed the camera UI, reverted the Wi-Fi and cellular connectivity levels in the status bar back to Wi-Fi left, added themed notifications, added a battery animation in Settings: Battery, a new icon and darker background for the Clock app, and a teardrop icon shape for apps.

On August 18, 2017, Google launched an eclipse-themed teaser website, stating the release date and name unveiling of Android O as August 21, coinciding with the solar eclipse in the US.The name ultimately turned out to be "Oreo", as a partnership between Google and Nabisco, the producers of the world-famous cookie.Factory images were made available for compatible Nexus and Pixel devices later that day.