Aerobic glycolysis (the Warburg effect) is a metabolic hallmark of activated T cells, and has been implicated in augmenting effector T cell responses including expression of the pro-inflammatory cytokine interferon (IFN)-γ via 3′ untranslated region (3′UTR)-mediated mechanisms. Here we show that lactate dehydrogenase A (LDHA) is induced in activated T cells to support aerobic glycolysis, but promotes IFN-γ expression independently of its 3′UTR. Instead, LDHA maintains high levels of acetyl-CoA to enhance histone acetylation and transcription of Ifng. Ablation of LDHA in T cells protects mice from immunopathology triggered by excessive IFN-γ expression or deficiency of regulatory T cells. These findings reveal an epigenetic mechanism by which aerobic glycolysis promotes effector T cell differentiation, and suggest that LDHA may be targeted therapeutically in autoinflammtory diseases.