The global rise of antibiotic-resistant bacteria has created an urgent need for alternative antimicrobial strategies. Bacteriophages, viruses that specifically infect bacteria, have re-emerged as promising therapeutic and biomedical tools. This review summarizes current knowledge on bacteriophage biology, their role in antibacterial therapy, applications in combating antimicrobial resistance, diagnostic uses, and emerging clinical perspectives. By synthesizing recent findings, this article highlights the medical significance of bacteriophages and discusses challenges and future directions for their integration into modern healthcare. Antibiotic resistance is considered one of the most serious threats to global public health. The reduced efficacy of conventional antibiotics has prompted renewed interest in bacteriophages as biological agents capable of targeting pathogenic bacteria. Although phage therapy was explored before the antibiotic era, scientific advances in molecular biology and genomics have revitalized research into bacteriophage-based medical applications. This review aims to provide a comprehensive overview of bacteriophages and their importance in therapeutic and clinical medicine. Bacteriophages are viruses composed of nucleic acids enclosed in protein structures that enable them to recognize and infect bacterial hosts. They exhibit remarkable host specificity, binding to particular receptors on bacterial cell surfaces. Phages generally follow either a lytic or lysogenic life cycle. Lytic phages replicate within the bacterial cell and cause its destruction, a property that underpins their therapeutic value. Understanding phage–bacteria interactions is fundamental to the development of safe and effective medical applications. Phage therapy involves the administration of bacteriophages to treat bacterial infections. Numerous studies have demonstrated the effectiveness of lytic phages against a wide range of pathogenic bacteria, including multidrug-resistant strains. Compared to antibiotics, phages offer several advantages, such as high specificity, minimal disruption to normal microbiota, and the ability to self-amplify at the site of infection. Clinical use of phage therapy has shown promising outcomes in cases where conventional treatments failed. Bacteriophages represent a strategic approach to combating antimicrobial resistance. Their mechanisms of bacterial killing differ fundamentally from those of antibiotics, allowing them to bypass common resistance pathways. Additionally, phage-derived enzymes, including endolysins and depolymerases, have been investigated as standalone antimicrobial agents. Combined phage–antibiotic therapies have demonstrated synergistic effects, enhancing bacterial clearance and reducing the likelihood of resistance development. Beyond therapeutic use, bacteriophages play an increasingly important role in medical diagnostics. Phage-based detection systems enable rapid and accurate identification of bacterial pathogens in clinical samples. Genetically engineered phages have been employed as biosensors and imaging tools, improving diagnostic precision. Furthermore, bacteriophages contribute significantly to biomedical research, supporting advancements in molecular genetics, vaccine development, and gene delivery systems. Bacteriophages offer a versatile and effective solution to many challenges facing modern medicine, particularly antibiotic resistance. Their therapeutic, diagnostic, and research applications underscore their growing importance in healthcare. As scientific and clinical understanding expands, bacteriophages are likely to become integral components of future antimicrobial strategies.