Injectable biopolymer-based hydrogels have emerged as a powerful class of biomaterials designed for minimally invasive therapeutic strategies in modern medicine. These smart hydrogels, derived from natural biopolymers, such as alginate, chitosan, gelatin, hyaluronic acid, and collagen, offer unique advantages, including biocompatibility, biodegradability, and the ability to mimic the extracellular matrix. This review provides a comprehensive overview of recent advancements in the design, crosslinking mechanisms, and biofunctionality of injectable hydrogels tailored for targeted drug delivery and tissue regeneration. Special attention is given to their role in in situ gelling systems, cancer therapy, musculoskeletal repair, and neural regeneration. Challenges related to mechanical strength, degradation control, and clinical translation are also discussed, along with future perspectives for scalable manufacturing and regulatory approval.