Sirt6 has been implicated as a key regulator in aging-related diseases, including osteoarthritis. However, its functional role and molecular mechanism in chondrocyte senescence and osteoarthritis pathophysiology remain largely undefined. Here we show that Sirt6 deficiency exaggerates chondrocyte senescence and osteoarthritis progression, whereas intra-articular injection of adenovirus-Sirt6 markedly attenuates surgical destabilization of medial meniscus-induced osteoarthritis. Mechanistically, Sirt6 can directly interact with STAT5 and deacetylate STAT5, thus inhibiting the IL-15/JAK3-induced STAT5 translocation from cytoplasm to nucleus, which inactivates IL-15/JAK3/STAT5 signaling. Mass spectrometry revealed that Sirt6 deacetylated conserved lysine 163 on STAT5. Mutation of lysine 163 to arginine in STAT5 abolished the regulatory effect of Sirt6. In vivo, specific ablation of Sirt6 in chondrocytes exacerbated osteoarthritis. Pharmacological activation of Sirt6 substantially alleviated chondrocyte senescence. Taken together, Sirt6 attenuates chondrocyte senescence by inhibiting IL-15/JAK3/STAT5 signaling. Targeting Sirt6 represents a promising new approach for osteoarthritis.