Water vapor in the lower stratosphere may play significant roles in the atmospheric radiative budget and atmospheric chemistry; hence it is important to understand its transport process. The possibility of water vapor transport from the troposphere to the stratosphere by deep convection is investigated using three-dimensional, nonhydrostatic, quasi-compressible simulations of a Midwest severe thunderstorm. The results show that the breaking of gravity waves at the cloud top can cause cloud water vapor to be injected into the stratosphere in the form of plumes above a thunderstorm anvil. Meteorological satellites and aircrafts have observed such plumes previously, but the source of water vapor and the injection mechanism were not identified. The present results reveal that there are two types of plumes, anvil sheet plumes and overshooting plumes, in this injection process and that the process is diabatic. A first-order estimate of this plume transport of water vapor per day from the upper troposphere to the lower stratosphere was made assuming that all thunderstorms behave the same as the one simulated. Other trace chemicals may also be similarly transported by the same mechanism.