The quasi-biennial oscillation (QBO) is the dominant mode of variability of the tropical lower stratosphere on monthly to interannual time scales. The oscillation consists of alternating downward propagating easterly and westerly shear zones, with a mean period of about 28 months. While the QBO has been observed for over 60 years and its basic mechanism is understood, it still remains a modeling challenge for many general circulation models (GCMs). There is evidence that the QBO affects the tropical troposphere and also the stratosphere and troposphere at higher latitudes, via teleconnections. Since the QBO is itself highly predictable, these teleconnections can lead to increased predictability on seasonal and subseasonal time scales in these regions, for example, of the North Atlantic Oscillation (NAO) or of tropical precipitation associated with the Madden–Julian oscillation (MJO). During the Northern Hemisphere winter of 2015/16, the regular QBO cycle was disrupted by an anomalous upward displacement of the prevailing westerly phase and the emergence of easterlies near 40 hPa; this was the first interruption of the QBO in the observed record. This interruption, together with increasing greenhouse gases and warming sea surface temperatures, prompt questions about how the QBO and its impacts may change in the future. In this session, we invite abstracts related to all aspects of the QBO, including modeling and predictability of the QBO, climate change and the QBO, the 2015/16 QBO disruption, and the impacts of the QBO on other regions of the atmosphere.