The CDC 6600 was the flagship of the 6000 series of mainframe computer systems manufactured by Control Data Corporation. Generally considered to be the first successful supercomputer, it outperformed the industry's prior recordholder, the IBM 7030 Stretch, by a factor of three. With performance of up to three megaFLOPS, the CDC 6600 was the world's fastest computer from 1964 to 1969, when it relinquished that status to its successor, the CDC 7600.

The first CDC 6600s were delivered in 1965 to Livermore and Los Alamos. They quickly became a must-have system in high-end scientific and mathematical computing, with systems being delivered to Courant Institute of Mathematical Sciences, CERN, the Lawrence Radiation Laboratory, and many others. At least 100 were delivered in total.

A CDC 6600 is on display at the Computer History Museum in Mountain View, California. The only running CDC 6000 series machine has been restored by Living Computers: Museum + Labs.