Computational Fluid Dynamics (CFD) simulations of solid–liquid flows in stirred tanks are feasible with appropriate closure models. However, no systematic assessment of different models has appeared yet because of lacking validation data. The present study accumulates a “CFD-grade” database on solid–liquid two-phase flow experiments in a stirred tank (diameter = 90 mm), including single-phase flows for comparison. The velocity fields of the liquid and solid phases are measured with Particle Image Velocimetry and Particle Shadow Velocimetry, respectively. The experiments cover a range of density ratios, particle diameters, solid volume fractions and impeller rotation speeds. The mean and fluctuating liquid and solid velocities are obtained by time-averaging and angle-resolved averaging, as well as the time-averaged local solid fraction. The experimental data for the single-phase flows is compared with CFD simulations which show reasonably good predictions. A systematic assessment of CFD models for solid–liquid flows will appear as a sequel.