C-Stoff ("C substance") was a reductant used in bipropellant rocket fuels developed by Helmuth Walter Werke in Germany during World War 2. It was developed for use with T-Stoff (a high test peroxide), which could also be ignited by a simple catalyst solution, Z-Stoff.

The proportions of the components in C-Stoff were developed to catalyse the decomposition of T-Stoff, promote combustion with the oxygen released by the decomposition, and sustain uniform combustion through sufficient quantity of the highly reactive hydrazine. The combination of the C-Stoff, used as a rocket fuel, with the T-Stoff used as the oxidizer, often resulted in spontaneous explosion from their combined nature as a hypergolic fuel combination, necessitating strict hygiene in fueling operations; there were numerous catastrophic explosions of the Messerschmitt Me 163 aircraft which employed this fuel system. Another hazard was toxicity to humans of each of the fuels.

See also

• List of Stoffs