Fluidized bed reactors (FBRs) are crucial in the chemical industry, serving essential roles in gasoline production, manufacturing materials, and waste treatment. However, traditional up-flow FBRs have limitations in applications where rapid kinetics, catalyst deactivation, sluggish mass/heat transfer processes, particle erosion or agglomeration (clustering) occur. This review investigates multifunctional FBRs that can function in multiple ways and intensify processes. These reactors can reduce reaction steps and costs, enhance heat and mass transfer, make processes more compact, couple different phenomena, improve energy efficiency, operate in extreme fluidized regimes, have augmented throughput, or solve problems inherited by traditional reactor configurations. They address constraints associated with conventional counterparts and contribute to favorable energy, fuels, and environmental footprints. These reactors can be classified as two-zone, vortex, and internal circulating FBRs, with each concept summarized, including their advantages, disadvantages, process applicability, intensification, visualization, and simulation work. This discussion also includes shared considerations for these reactor types, along with perspectives on future advancements and opportunities for enhancing their performance.