Viral reverse genetics involves the process of generating synthetic viruses from purified DNA or RNA, enabling the artificial engineering of viral genes. In recent decades, viral reverse genetics has been effectively implemented for numerous viruses that pose significant threats to public health and the global economy. Viral reverse genetics techniques enable researchers to elucidate the molecular mechanisms of viral infection and transmission, trace viral evolution and replication, and study the impact of viral mutations on the virus life cycle. In this chapter, we describe a general reverse genetic strategy for rescuing DNA and RNA viruses.