Ionic Liquid Nanoparticles (ILNPs) have gained significant attention as advanced catalytic materials due to their unique physicochemical properties, which offer remarkable advantages over conventional catalysts. Their tunable composition, high thermal and chemical stability, negligible vapor pressure, and ability to dissolve a wide range of reactants make them highly suitable for catalytic applications. This chapter explores the applications of ILNPs in catalysis, emphasizing their role in homogeneous and heterogeneous catalytic systems and their impact on modern chemical transformations. ILNPs have demonstrated exceptional efficiency in various catalytic processes, including organic synthesis, biomass conversion, environmental catalysis, and industrial reactions. Moreover, ILNPs have shown promise in biomass valorization, facilitating the conversion of renewable feedstocks into biofuels and high-value chemicals. In environmental applications, ILNP-based catalysts contribute to wastewater treatment, CO2 capture, and pollutant degradation, aligning with sustainable and green chemistry principles. A key focus of this chapter is the mechanistic understanding of ILNP-driven catalysis, including reactant–catalyst interactions, surface modifications, and electronic effects that govern catalytic efficiency. Research efforts are continuously evolving to optimize ILNP-based catalytic systems by improving their structural robustness and integrating them into continuous-flow and large-scale industrial processes. This chapter provides a comprehensive overview of the synthesis, applications, challenges, and future perspectives of ILNPs in catalysis, highlighting their transformative role in advancing efficient and sustainable chemical processes.