Siri is a virtual assistant with a voice-controlled natural language interface that uses sequential inference and contextual awareness to help perform personal tasks for iOS users.

Spun out of the DARPA-funded CALO project, Siri was initially developed by Dag Kittlaus and his team of SRI International as an iPhone app. Apple bought Siri in 2010; in October 2011, the company re-released it as part of iOS 5. Siri is available on iOS, macOS, watchOS, homeOS, and tvOS, though the service has different features available depending on the platform.