Hydrogels are three-dimensional (3D) network materials composed of natural or synthetic hydrophilic polymers. Their porous structure and high-water content confer unique properties and potential applications in a variety of areas. In the biomedical field, hydrogels have been extensively investigated as carriers for drug delivery and as scaffolds for tissue engineering and regenerative medicine. However, the high water content and weak intermolecular forces within the polymer network lead to softness and inadequate mechanical properties, such as rapid degradation, easy deformation, and low tensile strength. These limitations restrict the use of unmodified hydrogels in applications requiring long-term structural integrity (e.g., sustained drug protection and release, tissue healing) and the ability to withstand mechanical stresses. Therefore, the composition and structure of hydrogels must be carefully optimized to match their intended applications. One approach to address the hydrogel durability and performance is the covalent crosslinking of the polymer chains within the gel matrix. Dual networks made of interpenetrating polymers have also been explored. Another strategy is to construct hybrid hydrogels in which nano-objects are homogeneously integrated in the gel matrix. Most examples of this type of hydrogels involve the physical dispersion of nanoparticles (NPs), which are trapped in the porous continuous polymer network, although nano-objects can also act as crosslinking agents. Due to the incorporation of NPs into the hydrogel matrix, the resulting hybrid nanocomposite hydrogels undergo structural reinforcement and might also acquire additional properties. For instance, nano-objects can endow hydrogels with sustained drug release properties, often triggered by endogenous or exogenous stimuli. Nano-objects may also confer theranostic functionalities, or conductivity and adhesiveness which are valuable properties for specific applications. The appeal of this approach lies in its versatility as it allows the formulation of a wide variety of hybrid nanocomposite hydrogels by combining different hydrogel matrices and different NP types. The ability to adjust the functionalization of these components can further enhance the versatility of hybrid hydrogels. Numerous review articles have been describing hybrid nanocomposite hydrogels, covering the main formulation approaches and fabrication methods as well as some general biomedical, environmental, and industrial applications. Among them, excellent reviews covering their application in oncology and infectious diseases, wound healing, bone regeneration, cartilage and cardiac tissue engineering have also been published.