This contribution presents the inclined rotating fixed-bed reactor as a new chemical reactor concept for heterogeneous multiphase reactions. By combining the inclined and rotating operation of a fixed-bed, this new process intensification equipment allows for flow regime adjustment at fixed flow rates and overcomes liquid maldistribution. A highly integrated, compact gamma-ray computed tomography system for the non-invasive investigation of the flow regimes in the new reactor is presented, as well. Based on systematic flow experiments, flow regime maps for the inclined rotating fixed-bed reactor are generated for the first time and the effects of varying physico-chemical properties of the liquid phase on the flow regimes are discussed.