Perineal hygiene (external genitalia) is the maintenance of individual hygiene and health carried out in daily life so as to avoid reproductive disorders and obtain physical and psychological well-being and improve health status. The purpose of this study was to determine the relationship between perineal hygiene knowledge and perineal hygiene behavior in adolescent girls in Class VII SMPN 1 Gedeg, Gedeg District, Mojokerto Regency. This research design uses correlational analytic with cross sectional approach. The population of this research is all the students of class VIII SMPN 1 GEDEG, Gedeg District, Mojoketo Regency as many as 80 students using purposive sampling technique. Data were collected using a questionnaire instrument, processed by editing, coding, scoring, tabulating. The results showed that most of the knowledge of perineal hygiene was good with positive perineal hygiene behavior as many as 54 respondents (67.5%). By using the Spearmen Rho statistical test, the results obtained value (0.000) < (0.05), meaning that there is a relationship between Perineal Hygine Knowledge and Perineal Hygine Behavior in Adolescent Girls at SMPN Gedeg Kec. Gedeg Kab. Mojokerto. The level of knowledge of good perineal hygiene is the more positive the behavior of young women in maintaining their external genital organs, besides knowledge and attitudes will be the basis for the formation of one's morals so that in a teenager ideally there is harmony between knowledge and attitude, where attitudes will be formed after someone gets knowledge.