Which version of macOS introduced Mission Control?

Mission Control was introduced in Mac OS X 10.7 Lion. Released in 2011, Lion combined and renamed several existing window-management features, chiefly Exposé, Spaces, and Dashboard, into a unified overview called Mission Control.

Mission Control lets users see open windows, switch between applications, and manage multiple virtual desktops, called Spaces. It also supports multiple displays and provides App Exposé, which focuses on windows belonging to the current application. On newer Macs, users can usually open it with the F3 key, a trackpad gesture, or a configured hot corner.

The feature was not created from nothing in Lion. Exposé first appeared in Mac OS X 10.3 Panther in 2003, giving users a way to reveal and select windows. Spaces became a separate multiple-desktop feature in Mac OS X 10.5 Leopard. Lion's key change was to bring these ideas together under one interface and name; later releases adjusted window grouping, backgrounds, and other visual details.