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Depleting regulatory T cells (T-reg cells) to counteract immunosuppressive features of the tumor microenvironment (TME) is an attractive strategy for cancer treatment; however, autoimmunity due to systemic impairment of their suppressive function limits its therapeutic potential. Elucidating approaches that specifically disrupt intratumoral T-reg cells is direly needed for cancer immunotherapy. We found that CD36 was selectively upregulated in intrautumoral T-reg cells as a central metabolic modulator. CD36 fine-tuned mitochondrial fitness via peroxisome proliferator-activated receptor-beta signaling, programming T-reg cells to adapt to a lactic acid-enriched TME. Genetic ablation of Cd36 in T-reg cells suppressed tumor growth accompanied by a decrease in intratumoral T-reg cells and enhancement of antitumor activity in tumor-infiltrating lymphocytes without disrupting immune homeostasis. Furthermore, CD36 targeting elicited additive antitumor responses with anti-programmed cell death protein 1 therapy. Our findings uncover the unexplored metabolic adaptation that orchestrates the survival and functions of intratumoral T-reg cells, and the therapeutic potential of targeting this pathway for reprogramming the TME., Tumor environments are highly acidic due to high concentrations of lactic acid. Ho and colleagues report that tumor-infiltrating regulatory T cells adapt to this tumor environment by upregulating expression of CD36, which allows them to use fatty acids to fuel their metabolism.