The news comes just a week after the carrier dispatched the update for the huge Nokia Lumia 1520, and it brings a host of new features to Microsoft's mobile operating system.
There's now room to pack more Live Tiles on your home screen, the new Action Center hosts common settings and notifications, and the Word Flow keyboard lets you swipe your finger across the keyboard to send messages. And who could forget Cortana, Microsoft's answer to Siri and Google Now?
Of course there's plenty more besides -- be sure to check out our review of Windows Phone 8.1 for the full rundown on what's new.
Ready to get started? Grab your phone, head on over to the settings app, and tap "Phone Update" to get the over-the-air update. The file size varies by phone -- 200MB on the 520, 450MB on the 925 -- so be sure you have enough free space available.
AT&T also recommends making sure your battery is at least 50 percent charged. Check out the company's Software Update support page if you've got any more questions.