Abstract : The gut microbiome plays a crucial role in the regulation of metabolism, immune responses, and neuroendocrine communication in the human body. In recent years, a growing body of evidence has highlighted its association with the development and progression of chronic diseases, including obesity, type 2 diabetes, cardiovascular diseases, chronic kidney disease, and depressive disorders. Increasingly, it is emphasized that the key factor is not merely changes in the taxonomic composition of the gut microbiota, but rather disturbances in its metabolic and immunomodulatory functions. The aim of this narrative review is to provide a concise synthesis of current knowledge on the role of the gut microbiome in selected chronic diseases, with particular emphasis on underlying pathophysiological mechanisms, clinical relevance, and the limitations of contemporary microbiome-targeted therapies. Special attention is given to the boundaries of current evidence and the risk of overinterpretation of microbiome research findings.