– "System 1", released in 1984

Macintosh System Software

– released between 1985 and 1987

System Software 2, 3, and 4

– released in 1987

System Software 5

– released in 1988

System Software 6

– released in 1991

System 7 / Mac OS 7.6

– released in 1997

Mac OS 8

– final major version, released in 1999

Mac OS 9