Monoclonal antibodies (MAbs) are an old immunological tool with applications in the fields of immunology, biotechnology, biochemistry, and applied biology. Production of monoclonal antibodies using hybridoma technology was discovered in 1975 by Georges Kohler of West Germany and Cesar Milstein of Argentina. Modern-day research on MAbs from laboratories worldwide is revealing additional applications in diverse branches of sciences. Recently, MAbs have been widely applied in the field of clinical medicine. Currently, MAbs account for one-third of all the new therapeutic treatments for breast cancer, leukemia, arthritis, transplant rejection, asthma, and psoriasis, with many more late-stage clinical trials being conducted. In this review, we outline the (i) production of MAbs, (ii) application of MAbs, (iii) antibody engineering, and (iv) pharmaceutical application of MAbs. The future prospect of this review lies in the applicability of monoclonal antibodies as a molecule for understanding and monitoring the biology of disease and its role in research, clinical, diagnostic, analytical, and pharmaceutical applications.