Regulatory T (T) cells modulate several aging-related liver diseases. However, the molecular mechanisms regulating T function in this context are unknown. Here we identified a long noncoding RNA, Altre (aging liver T-expressed non-protein-coding RNA), which was specifically expressed in the nucleus of T cells and increased with aging. T-specific deletion of Altre did not affect T homeostasis and function in young mice but caused T metabolic dysfunction, inflammatory liver microenvironment, liver fibrosis and liver cancer in aged mice. Depletion of Altre reduced T mitochondrial integrity and respiratory capacity, and induced reactive oxygen species accumulation, thus increasing intrahepatic T apoptosis in aged mice. Moreover, lipidomic analysis identified a specific lipid species driving T aging and apoptosis in the aging liver microenvironment. Mechanistically, Altre interacts with Yin Yang 1 to orchestrate its occupation on chromatin, thereby regulating the expression of a group of mitochondrial genes, and maintaining optimal mitochondrial function and T fitness in the liver of aged mice. In conclusion, the T-specific nuclear long noncoding RNA Altre maintains the immune-metabolic homeostasis of the aged liver through Yin Yang 1-regulated optimal mitochondrial function and the T-sustained liver immune microenvironment. Thus, Altre is a potential therapeutic target for the treatment of liver diseases affecting older adults.