原病毒（英语：provirus），又称前病毒，指一类侵入寄主细胞后，遗传因子借由逆转录并入寄主遗传物质内，会随着寄主细胞的子细胞遗传的病毒。所有被感染细胞后代的基因组中，均会有这种原病毒的遗传物质。这个过程被称为细胞的溶源化循环。

这个整体会造成潜在或显着的感染：

当寄主细胞的环境或健康状况变化时，潜在感染会转变为显着感染。此时原病毒开始直接转录自己的基因，而寄主细胞最终坏死，因为该细胞的蛋白质生产体系无法生产如此多的病毒。原病毒大概能以内源性逆转录酶病毒的形式破坏大约8%的人体基因。

A provirus is a virus genome that is integrated into the DNA of a host cell. In the case of bacterial viruses (bacteriophages), proviruses are often referred to as prophages.

This state can be a stage of virus replication, or a state that persists over longer periods of time as either inactive viral infections or an endogenous viral element. In inactive viral infections the virus will not replicate itself but through replication of its host cell. This state can last over many host cell generations.