<p>Bacteriophages, viruses that specifically target and lyse bacterial cells, were first discovered over a century ago. At present, as drug-resistant bacterial infections and cancer pose some of the greatest challenges to global health, phage therapy has emerged as a potential solution to both issues. This review focuses on the three critical steps involved in the development of phage therapy: phage isolation, host characterization, and assessment of therapeutic efficacy in both in vitro and in vivo models. The therapeutic potential of phage therapy is discussed across a range of infections, including pulmonary, gastrointestinal, dermal, and dental diseases, along with its application in treating various cancers, such as melanoma, glioblastoma, breast cancer, and colon cancer. Furthermore, this review highlights the distinct advantages of phage therapy over traditional treatments, as well as the challenges and limitations hindering its widespread adoption. Future prospects, including the need for personalized phage therapy and overcoming regulatory and safety hurdles, are also considered.</p>