Sex education is instruction on issues relating to human sexuality, including emotional relations and responsibilities, human sexual anatomy, sexual activity, sexual reproduction, age of consent, reproductive health, reproductive rights, safe sex, birth control and sexual abstinence. Sex education that covers all of these aspects is known as comprehensive sex education. Common avenues for sex education are parents or caregivers, formal school programs, and public health campaigns.

Traditionally, adolescents in many cultures were not given any information on sexual matters, with the discussion of these issues being considered taboo. Such instruction, as was given, was traditionally left to a child's parents, and often this was put off until just before a child's marriage. The progressive education movement of the late 19th century, however, led to the introduction of "social hygiene" in North American school curricula and the advent of school-based sex education. Despite early inroads of school-based sex education, most of the information on sexual matters in the mid-20th century was obtained informally from friends and the media, and much of this information was deficient or of dubious value, especially during the period following puberty, when curiosity