Functionalized organic-inorganic hybrids of ionic liquids (ILs) with Keggin polyoxometalate (POM) anions of heteropolyacids have received considerable attention in the catalytic study as homogeneous/heterogeneous catalysts owing to their combined unique structural flexibility of the POM anions and tunable behavior imparted by the ionic liquids to the organic-inorganic hybrid of POMs (IL-POM). This includes enhancement of thermal and chemical stability, acidity, surface activity, redox properties, etc. The attachment of Brønsted acidic sites such as -COOH or –SO3H on organic cations of the hybrid materials provides a strong acidic character that can make them appropriate for the replacement of non-recyclable liquid Brønsted acid catalysts in organic reactions. Hydrophobicity, reusability, recyclability, and productivity of these materials certainly satisfy the need for advanced organic synthesis. A large number of designable target-oriented hybrids have been studied as recyclable homogeneous/heterogeneous catalytic systems to explore their industrial values for oxidation and acid-catalyzed organic reactions. This chapter gives a brief introduction to the development of acidic ionic liquid-based POMs hybrid material with varied organic cations tethered with Brønsted acidic sites and their beneficial effects in catalytic organic reactions. The content of this report may provide enormous scope for the development of industrial-scale organic processes based on the IL-POMs hybrid catalysts.