http://www.techradar.com/news/android-oreo-finally-lands-on-the-oneplus-5

Android Oreo was supposed to arrive on the OnePlus 5 during December, but an unnamed bug held it up, however, it now seems the bug has been squashed, as Oreo has once again begun rolling out to OnePlus 5 handsets.

It’s a staged rollout, so you might not have it yet, but if not it should hit your phone soon as an OTA (over the air) update named OxygenOS 5.0.1.