Mucosal-associated invariant T (MAIT) cells are a subpopulation of innate-like T lymphocytes that recognize Vitamin B metabolites. Although MAIT cells provide rapid, innate-like responses, they are not pre-set and memory-like responses have been described following infections. The importance of metabolism for controlling these responses, however, is unknown. Our data indicate that different MAIT subsets have intrinsically distinct metabolic requirements. This metabolic diversity was already established in the thymus during MAIT cell development, and was maintained in peripheral tissues. Following pulmonary immunization with a Salmonella vaccine strain, mouse MAIT cells expanded as separate CD127-Klrg1+ and CD127+Klrg1- antigen-adapted populations that differed for their transcriptome, function and localization in lung tissue. These populations remained altered from steady-state for months as stable, largely separate MAIT cell lineages with enhanced effector programs and divergent metabolism. CD127+ MAIT cells engaged in an energetic, mitochondrial metabolic program, which was critical for their maintenance and IL-17A synthesis. This program was supported by high fatty acid uptake and mitochondrial oxidation and relied on highly polarized mitochondria and autophagy. After vaccination, CD127+ MAIT cells protected mice against Streptococcus pneumoniae infection. In contrast, Klrg1+ MAIT cells had dormant, but ready-to-respond mitochondria and depended instead on Hif1a-driven glycolysis for survival and cytokine production. They responded vigorously to the cytokines IL-12/18 and participated in protection from influenza virus. These metabolic dependencies may enable tuning of memory-like MAIT cell responses for vaccinations and immunotherapies.