Postbiotics, defined as bioactive compounds produced during microbial fermentation, have recently emerged as promising functional metabolites with potential health benefits. Unlike probiotics, which rely on live microorganisms, postbiotics encompass a diverse array of microbial-derived substances such as short-chain fatty acids (SCFAs), peptides, enzymes, cell wall fragments, and extracellular polysaccharides, which confer health benefits even in the absence of live bacteria. Accumulating evidence highlights their role in modulating gut microbiota composition, enhancing mucosal immunity, attenuating inflammation, and maintaining gut barrier integrity. Moreover, postbiotics are associated with potential therapeutic applications in metabolic disorders, inflammatory bowel disease (IBD), colorectal cancer, and infectious diseases. Their stability, safety profile, and ease of formulation position them as viable alternatives or adjuncts to probiotics and prebiotics. This review synthesizes current evidence on the biological mechanisms, clinical applications, and future perspectives of postbiotics, emphasizing their translational potential in gut health and disease management.