The eruption of the submarine Hunga Tonga Hunga Hapaii volcano on 15 January 2022 was associated with a powerful blast that injected sulfur and water to altitudes up to 58 km. In this study, we combine the data from various satellite instruments (MLS, OMPS-LP, CALIOP, SAGE III, Aeolus, COSMIC-2, ACE-FTS, GOES, Himawari), ground-based lidars at various locations, meteorological radiosoundings as well as model simulation using CLaMS chemistry-transport model to investigate the evolution of the stratospheric moisture and sulfate aerosol plume at a wide range of scales—from minutes and kilometres to monthly and planetary scale. We show that due to extreme altitude reach of the eruption, the volcanic plume has circumnavigated the Earth in only one week and dispersed nearly pole-to-pole in three months. The observations provide evidence for an unprecedented increase in the global stratospheric water mass by 13% as compared to climatological levels. As there are no efficient sinks of water vapour in the stratosphere, this perturbation is expected to persist several years. The eruption has also led to a 5-fold increase in the stratospheric aerosol load, the highest in the last three decades yet factor of 6 smaller than the previous major eruption of Mt Pinatubo in 1991. The unique nature and magnitude of the global stratospheric perturbation by the Hunga eruption ranks it among the most remarkable climatic events in the modern observation era. Given the expected longevity of the stratospheric humidity perturbation, the Hunga eruption can be said to have initiated a new era in stratospheric gaseous chemistry and particle microphysics with a wide range of potential long-lasting repercussions for the global stratospheric composition and dynamics. The eruption has thus provided a unique natural testbed, lending itself to studies of climate sensitivity to strong change in both stratospheric gaseous and particulate composition. Spanning more than one year, the satellite and ground-based observations available to-date enable the first accurate assessment of the annual-scale stratospheric aftermath of the Hunga Tonga eruption, uncovering its climate-altering capacity.