According to Wikipedia

macOS Sierra

macOS High Sierra

macOS Mojave

macOS Catalina

What is Apple’s operating system called?

Mac OS X was originally presented as the tenth major version of Apple’s operating system for Macintosh computers; current versions of macOS retain the major version number “10”. Previous Macintosh operating systems (versions of the classic Mac OS) were named using Arabic numerals, as with Mac OS 8 and Mac OS 9.

What is my Mac operating system?

First, click on the Apple icon in the top left corner of your screen. From there, you can click ‘About this Mac’. You’ll now see a window in the middle of your screen with information about the Mac you’re using. As you can see, our Mac is running OS X Yosemite, which is version 10.10.3.