Bacteriophages are bacterio-specific viruses that constitute a main portion of the environment. Bacteriophages inject their genome into the targeted bacterial cells and some of them can disrupt the metabolism of bacteria and cause bacterial cell disintegration. The application of bacteriophages to kill bacteria is known as bacteriophage therapy. Since bacteriophages target bacteria and are strain-specific, every bacteriophage/bacterial host pair is unique. They are believed to cause no harm to humans. An additional advantage of the strain-specific nature of bacteriophages is that they do not disrupt the beneficial natural flora in the body. Bacteriophage therapy in the West is not a recognized medicine at this time, and no products are registered. Some clinicians are turning to bacteriophage therapy for the treatment of antibiotic-resistant infections. Lack of adverse effects makes bacteriophage therapy ideal for use. Funding research, media attention, and the increased publication of articles helped in a widespread understanding of its therapeutic potential. The first prerequisite for the use of bacteriophage therapy is simply the availability of bacteriophages for treatment, which is often complicated at this stage of bacteriophage production. This includes providing access to all biologically active bacteriophages against the bacterial isolate of the patient and meeting regulatory criteria of purity, traceability, and characterization. A monophage preparation, which is a single bacteriophage, or a phage cocktail, which consists of a number of combined bacteriophages against one or more bacterial species may be used. Accordingly, the antibiotic resistance crisis brought back bacteriophage therapy as a potential complementary or alternative treatment. Bacteriophages are promising cheap antibacterials.