Understanding the costs and benefits of climate change mitigation and adaptation options is crucial to justify and prioritise future decarbonisation pathways to achieve net zero. Here, we quantified the co-benefits of decarbonisation for air quality and public health under scenarios that aim to limit end-of-century warming to 2ºC and 1.5ºC. We estimated the mortality burden attributable to ambient PM_2.5 exposure using population attributable fractions of relative risk, incorporating projected changes in population demographics. We found that implementation of decarbonisation scenarios could produce substantial global reductions in population exposure to PM_2.5 pollution and associated premature mortality, with maximum health benefits achieved in Asia around mid-century. The stringent 1.5ºC-compliant decarbonisation scenario (SSP1-1.9) could reduce the PM_2.5-attributable mortality burden by 29% in 2050 relative to the middle-of-the-road scenario (SSP2-4.5), averting around 2.9M annual deaths worldwide. While all income groups were found to benefit from improved air quality through decarbonisation, the smallest health benefits are experienced by the low-income population. The disparity in PM_2.5 exposure across income groups is projected to reduce by 2100, but a 30% disparity between high- and low- income groups persists even in the strongest mitigation scenario. Further, without additional and targeted air quality measures, low- and lower-middle-income populations (predominantly in Africa and Asia) will continue to experience PM_2.5 exposures that are over three times the World Health Organization (WHO) Air Quality Guideline.