A Bacterial Virus is a type of virus which infects bacteria and eventually kills them. Sometimes, they are also referred to as bacteriophage. Bacterial virus was first known circa 1915. Bacterial viruses are known to play a crucial role in the ecosystem. They are officially classified as viruses. However, to date, their structure is not yet fully understood because of its complex nature.

Bacterial viruses are useful in experiments especially in proving the replication of virus within the DNA through the processes called lytic cycle and lysogenic cycle. To date, it is still being studied whether or not these bacterial viruses can be used for therapeutic purposes. In the near future, these would be helpful in fighting certain types of bacterial infection.