IOS may refer to any of the following:
1. Originally known as the iPhone OS, iOS is the operating system that runs on Apple iPhone, Apple iPad, and Apple iPad Touch devices that was first introduced by Steve Jobs during the 2007 WWDC introducing the iPhone. iOS is the second-most popular platform for mobile devices, only slightly edged out by Android.
2. Short for Input/Output Supervisor, IOS is a program developed by Microsoft that watches over the interaction of the file system and computer drivers.
3. Short for Internetworking operating system, IOS was developed by Cisco and is used to manage and control network routers, switches, and other network devices.