Since their discovery over a century ago, thousands of types of bacteriophages have been characterized which makes them the largest virus group known so far. The vast majority of the known bacteriophages are tailed and contain double-stranded DNA. However, culture independent molecular approaches have revealed that bacteriophages occur in a much larger diversity and in high abundance in essentially all environments on Earth, ranging from marine waters and soils, the deep biosphere or the human gut. In fact, >90% of the bacteriophages in certain environments are still unknown. At present, only a limited fraction of the existing bacteriophage diversity is maintained in public collections worldwide, which provide the quality controlled and documented cultures that are needed for scientific studies of bacteriophage biology. The phage collection of the Leibniz Institute DSMZ offers a diverse collection of bacteriophages that is continously extended based on diversity by acquiring members of new taxonomic groups, special phage collections from retiring scientists or by isolating phages in DSMZ projects.