Which macOS version introduced the "Siri" voice assistant?

macOS Sierra was the first macOS version to introduce the Siri voice assistant.

Apple added Siri to macOS 10.12 Sierra, released on September 20, 2016. On a Mac, users could invoke Siri from the Dock, menu bar, or a keyboard shortcut. Its results appeared in a window and could be pinned to Notification Center or dragged into other applications.

Siri on the Mac was adapted for desktop tasks rather than simply copied from the iPhone. It could search for files, send messages, look up information, adjust settings, and help locate documents. Sierra also introduced other major features, including Universal Clipboard, Auto Unlock with Apple Watch, and iCloud storage options for Desktop and Documents folders.

The naming can cause confusion because Siri had already arrived on iPhone with iOS 5 in 2011. Sierra was specifically the milestone for Apple’s Mac operating system. OS X El Capitan came immediately before it and did not include the built-in assistant.