Back&aim: Many studies have characterized the short-term association between ozone and mortality in different settings, but mostly across limited geographical areas and using different methodological approaches. In this study, we aimed at comprehensively assessing short-term ozone-related mortality associations in a multi-country analysis.Method: We collected daily mortality and air pollution data (ozone, O3, and particulate matter, PM10) from 245 locations in 16 countries (Australia, Brazil, Canada, Chile, Columbia, France, Japan, South Korea, Mexico, Portugal, Spain, Sweden, Switzerland, Taiwan, Thailand, and United States), included in the Multi-City Multi-Country Collaborative Research Network. We applied a two-stage time-series design. First, we modelled mortality-ozone associations across 21 days of lag using quasi-Poisson regression and distributed lag linear models (DLMs). Second, we performed a multilevel multivariate meta-regression to obtain pooled associations across locations nested within country. Best linear unbiased predictions (BLUPs) were derived at both location and country levels. We estimated season-specific ozone-related mortality through time-varying interaction DLMs.Results: On average, an increase in 10 μg/m3 in ozone was associated with a 0.6% increase in mortality risk [95%CI: 0.3 to 0.8%]. The positive association was lagged and persisted during the following 7 days. Country-specific BLUPs ranged between 0.2%[-0.05 to 0.5] in Brazil to 0.8%[0.5 to 1.2] in the US. The ozone-related mortality association was significantly larger in winter [0.8%, 0.5 to 1.0] vs summer [0.5%, 0.4 to 0.7]. Results were robust to sensitivity analyses, such as multi-pollutant models.Conclusion: This represents the largest epidemiological study on health effects of ozone. By using a common advanced statistical framework, we provide robust evidence on the association with all-cause mortality in different locations across the globe.On behalf of the MCC Network