Dietary restriction (DR) without malnutrition encompasses numerous regimens with overlapping benefits including longevity and stress resistance, but unifying nutritional and molecular mechanisms remain elusive. In a mouse model of DR-mediated stress resistance, we found that sulfur amino acid (SAA) restriction increased expression of the transsulfuration pathway (TSP) enzyme cystathionine γ-lyase (CGL), resulting in increased hydrogen sulfide (H₂S) production and protection from hepatic ischemia reperfusion injury. SAA supplementation, mTORC1 activation, or chemical/genetic CGL inhibition reduced H₂S production and blocked DR-mediated stress resistance. In vitro, the mitochondrial protein SQR was required for H₂S-mediated protection during nutrient/oxygen deprivation. Finally, TSP-dependent H₂S production was observed in yeast, worm, fruit fly, and rodent models of DR-mediated longevity. Together, these data are consistent with evolutionary conservation of TSP-mediated H₂S as a mediator of DR benefits with broad implications for clinical translation.