Genital herpes is a sexually transmitted disease (STD) caused by the herpes simplex virus (HSV). There are two types of HSV called HSV-1 and HSV-2 and while either can cause genital herpes, most cases are caused by HSV-2. In many cases, genital herpes causes no symptoms at all, but when symptoms do occur they include painful blisters or sores on the genitals and rectum. The HSV virus may stay in the body indefinitely so some people may experience recurrent outbreaks of disease symptoms. When symptoms return, they tend to be milder and briefer than during the first outbreak and their frequency usually decreases with time. There is no cure for genital herpes.

Genital herpes infections are very common in the United States although the prevalence has decreased in the past decade. Still, at least 45 million people, one out of every five adolescents and adults in the country, are infected with genital herpes. Women are more commonly infected than men, perhaps because it is easier for males to transmit the disease to females than vice versa.

HSV-1, while it can cause genital herpes, is more commonly associated with oral herpes (also known as cold sores).