The Chippewa Operating System (COS) is a discontinued operating system developed by Control Data Corporation in 1964[1] for the CDC 6600, generally considered the first supercomputer in the world.

[2] The Chippewa was initially developed as an experimental system, but was then also deployed on other CDC 6000 machines.

[3] The Chippewa was a rather simple job control oriented system derived from the earlier CDC 3000.

Its design influenced the later CDC Kronos and SCOPE operating systems.

[4][3] Its name was based on the Chippewa Falls research and development center of CDC in Wisconsin.