Hydrogen is currently assessed as a future clean fuel in a hydrogen economy. However, one key problem with implementing a full‐scale hydrogen economy is hydrogen storage (as hydrogen is highly compressible and volatile). One solution for this problem is hydrogen geo‐storage, where compressed hydrogen is injected into geological formations, and the hydrogen can be withdrawn again at any time. However, there is a serious lack of data for realistic geologic conditions, including for hydrogen‐rock wettability, which is proven to determine injectivities, withdrawal rates, storage capacities, and containment security. We thus measured this parameter at various geo‐storage conditions. For a realistic storage scenario in a deep sandstone aquifer, we found that the rock (quartz) was weakly water‐wet or intermediate‐wet. Increasing pressure, temperature, and organic surface concentration increased hydrogen wettability. This study, thus, provides fundamental data and aids in the industrial‐scale implementation of a future hydrogen economy.