Large-scale atmospheric transport and mixing play a key role in shaping the global distributions of chemical species and their responses to future climate change. In particular, transport and mixing of mass and chemical species (e.g., water vapor, ozone, aerosols) in the upper troposphere and stratosphere have important implications for stratospheric ozone chemistry, general atmospheric circulation, and surface climate. This session will highlight recent advances in our understanding of transport and mixing in the upper troposphere and stratosphere on a wide range of temporal and spatial scales, to better quantify the impacts of these processes on past, present, and future climate. Examples of relevant topics include the variability of and modulation by the Brewer–Dobson circulation and the quasi-biennial oscillation; stratosphere–troposphere exchange and its effects on stratospheric and tropospheric chemistry, isentropic exchange in tropopause folds, subtropical transport barriers, and the tropical pipe model; and the role of the Asian monsoon system in the upper troposphere and lower stratosphere region. Modeling, theoretical, and observational studies are all encouraged.