Mixed plastic waste treatment has long been a significant challenge due to complex composition and sorting costs. In this study, we have achieved a breakthrough in converting mixed plastic wastes into a single chemical product using our innovative single-atom catalysts for the first time. The single-atom Ru catalyst can convert ∼90% of real mixed plastic wastes into methane products (selectivity >99%). The unique electronic structure of Ru sites regulates the adsorption energy of mixed plastic intermediates, leading to rapid decomposition of mixed plastics and superior cycle stability compared to traditional nanocatalysts. The global warming potential of the entire process was evaluated. Our proposed carbon-reducing process utilizing single-atom catalysts launches a new era of mixed plastic waste valorization.