Abstract It is well known that some pathogenic cells have enhanced glycolysis; the regulatory network leading to increased glycolysis are not well characterized. In this study, we show that CNS-infiltrated pathogenic TH17 cells from diseased mice specifically upregulate glycolytic pathway genes compared with homeostatic intestinal TH17 cells. Bioenergetic assay and metabolomics analyses indicate that in vitro–derived pathogenic TH17 cells are highly glycolytic compared with nonpathogenic TH17 cells. Chromatin landscape analyses demonstrate TH17 cells in vivo that show distinct chromatin states, and pathogenic TH17 cells show enhanced chromatin accessibility at glycolytic genes with NF-κB binding sites. Mechanistic studies reveal that miR-21 targets the E3 ubiquitin ligase Peli1–c-Rel pathway to promote glucose metabolism of pathogenic TH17 cells. Therapeutic targeting c-Rel–mediated glycolysis in pathogenic TH17 cells represses autoimmune diseases. These findings extend our understanding of the regulation TH17 cell glycolysis in vivo and provide insights for future therapeutic intervention to TH17 cell–mediated autoimmune diseases.