Transgenic animal models are crucial tools in the modern biomedical research that have been successfully used for translating basic laboratory research into clinical applications. The chapter comprehensively describes animal models, particularly focusing on the transgenic animals used to study human diseases, drug development and for therapeutic interventions. The steps involved in generating transgenic animals, which include transgene preparation, transgene delivery methods, techniques such as DNA microinjection, embryonic stem cell manipulation, germ cell-mediated transgenesis, testis-mediated gene transfer, and somatic cell nuclear transfer, have been discussed in detail. Moreover, it highlights the application of transgenic animal models in functional genomics, drug discovery, disease modeling, and xenotransplantation. At last, the chapter outlines the ethical considerations governing the use of transgenic animals in biological research.