Explosive volcanic eruptions can loft ash, gases and water into the stratosphere, which affects both human activities and the climate. Using geostationary satellite images of the January 2022 Hunga-Tonga volcano eruption we find that the volcanic cloud produced by this volcano reached an altitude of 57km at its highest extent. This places the cloud in the lower mesosphere and provides the first observational evidence of a volcanic eruption injecting material through the stratosphere and directly into the mesosphere. We then discuss potential implications of this injection and suggest that the altitude reached by plumes from previous eruptions, such as Pinatubo in 1991, are very likely to be underestimated.