Centaur G and G' were redesigned Centaurs for Shuttle launch, with larger diameter tanks. The 4.3m diameter, 6m long G and 4.3m dia, 9.0m long G-prime were sized for the payload bay. The Shuttle-Centaur program was cancelled shortly before first launch. Two G' stages had been built, and one G was under construction. A third G' was planned for Magellan.
The CISS (Centaur Integrated Support System) was a cradle provided in the STS payload bay to support the stage.
| Centaur | Payload | 1986 Status |
| SC-1 (G') | Galileo | VPF testing at KSC |
| SC-2 (G') | Ulysses | Fuelling tests at CC LC36A |
| SC-3 (G) | DoD | Early fabrication |