Oncolytic virotherapy is a new strategy to reduce tumor burden through selective virus replication in rapidly proliferating cells. The nature of viral delivery, infection, and replication makes oncolytic virotherapy valuable for treating cancer patients, especially those with inoperable tumors. Oncolytic virotherapy is an emerging technology that uses engineer edviruses to treat malignancies. Viruses can be designed with biological specificity to infect cancerous cells preferentially, and to replicate in these cells exclusively. In this review, we describe the basis of oncolytic virotherapy, it’s history and the mechanisms by which oncolytic viruses destroy malignant cells and their selection. We also summarize various oncolytic virus and their properties along with oncolytic virotherapy clinical trials and their success rate. We conclude with current challenges and future research in oncolytic virotherapy.