<p>T cell metabolism constitutes a pivotal regulator of cellular states and disease progression. At the cellular level, the metabolic status of T cells directly governs their function and fate determination. Senescent T cells, for instance, exhibit fundamentally distinct metabolic signatures compared to effector T subsets, underscoring metabolic reprogramming as a critical mechanistic driver of T cell senescence. In pathological contexts, aberrant metabolic rewiring in T cells disrupts differentiation, function, and cellular survival, thereby contributing to disease onset and progression. Notably, the pathological accumulation of senescent T cells observed across chronic inflammatory and autoimmune diseases positions metabolism-driven T cell senescence as a key nexus linking metabolic dysregulation to clinical manifestations. Consequently, targeted modulation of T cell metabolism offers a dual therapeutic potential: direct intervention in cellular states (e.g., delaying senescent phenotypes) and synergistic amelioration of disease pathology through functional immune restoration. This Review summarizes the fundamental principles of T cell metabolic reprogramming, its causative role in propelling T cell senescence, and the dynamic interplay between metabolic dysfunction, T cell senescence, and disease pathogenesis. We specifically dissect these relationships in two immunologically divergent conditions—systemic lupus erythematosus (SLE, exemplifying hyperactive autoimmunity) and chronic infection (Chronic HIV infection, reflecting immune exhaustion)—to establish a mechanistic framework for developing metabolism-targeted immunotherapeutics that precisely restore T cell efficacy.</p>