In Mac OS terminology, Platinum was the Appearance Manager theme that Mac OS 8 and Mac OS 9 used.

Platinum retained many of the shapes from previous operating systems, like the shapes of window control widgets and of buttons. However, various shades of gray were used extensively throughout the interface, as opposed to previous themes that were solely black and white. Also, gradients of customizable colors were used for progress bars, and the colors of scroll thumbs could also be customized. Overall, the interface was much more advanced than previous black and white themes.

Mac OS X adopted the Aqua user interface style. Due to the numerous colors and lack of customizability, some people still prefer the platinum theme for Mac OS 9. Some platinum windows may still be seen in Mac OS X, because applications in the classic compatibility layer retain the platinum theme.