The nuclear envelope (NE) is essential for cellular homeostasis, yet its integrity declines with age, accelerating functional deterioration. Here we report a mitochondria-to-NE signalling pathway that safeguards NE integrity through redox-dependent lipid metabolism. In Caenorhabditis elegans, reducing mitochondrial ETC activity preserves NE morphology during ageing. This effect requires developmental mitochondrial superoxide, which downregulates SBP-1 (SREBP orthologue) and suppresses unsaturated fatty acid biosynthesis. The resulting reduction in unsaturated fatty acid levels limits lipid peroxidation, thereby preserving NE structure. Interventions targeting lipid peroxidation preserve NE integrity, extend lifespan in worms and ameliorate senescence-associated phenotypes in human fibroblasts and monkey cells mimicking Hutchinson–Gilford progeria syndrome disease. Our findings reveal a previously unrecognized role for mitochondrial superoxide as a protective developmental signal that programs long-term NE integrity. This work establishes lipid peroxidation control as a conserved strategy to delay nuclear ageing and highlights redox–lipid cross-talk as a therapeutic axis for healthy ageing.