This study was conducted to assess the knowledge of sexually transmitted infections as a predictor of public schools female adolescent’s sexual behaviour in Ikenne Local Government Area, Ogun State. A descriptive cross-sectional design was adopted for this study in which multi-stage sampling procedure was used to select 354 female adolescents from six public secondary schools. A self-administered questionnaire was used for data collection. The research instrument was validated by experts of Nursing Science and Tests & Measurement. Reliability of the instrument was tested by using Cronbach’s Alpha to determine internal consistency of the instrument. The values of 0.799 and 0.821 were gotten for knowledge of STIs and sexual behaviour scale respectively. Descriptive statistics were used to answer the research questions while inferential statistics of multiple regression and t-test analysis were used to test the hypotheses at 0.05 level of significance. The findings revealed that the knowledge level of the female adolescents about STIs was moderate but slightly below average while the female adolescents were sexually active. In addition, the result shows that the knowledge of STIs is negatively related to female adolescents’ sexual behaviour. Furthermore, the study found out that there was no significant difference between JSS and SSS female adolescents' sexual behaviour and knowledge of STIs. It was recommended among others that there is need for more aggressive efforts by all stakeholders - parents, teachers, nurses, government and non-governmental agencies to provide sexual information to adolescent girls. Keywords: Knowledge, Sexually Transmitted Infections, Female Adolescents, Sexual Behaviour,

This article has been published at www.easij.com, Issue: 3, Vol.#1, March, 2020.