There is intense interest in understanding the degree of damage caused by a pathogen. However, despite abundant evidence that effects of stressors can carry across generations, studies of pathogen virulence have focused almost exclusively on a single generation. Here, we describe transgenerational virulence, where parental exposure to a pathogen reduces offspring fitness. Daphnia host exposure to a microsporidian pathogen significantly reduced lifespan, and in some cases fecundity, of unexposed offspring. These effects carried to the granddaughters, which were smaller if the grandmother had pathogen exposure. A parameterized mathematical model translated these impacts to the population level, finding that transgenerational virulence often reduces host density. Given widespread prior evidence for transgenerational effects of predators, resources, and other factors, we propose that transgenerational virulence may be common.