**1. Introduction**

This chapter has been informed and validated by several published reports, literature, relevant international organizational publications, country-based materials, and ongoing initiatives (between 2017 and 2022 years). The reviewed documents included those related to young people's sexual and reproductive health against sexually transmitted infections (STIs) including human immunodeficiency virus (HIV), chlamydia, and teenage pregnancies among adolescents around the globe. Search engines for published research articles, reports, web pages, books, and or conferences preceding included google, google scholar, WBMED, and/or PUBMED. The criteria for the articles were set at not <2017 year of publications, and or only articles that addressed issues around STIs among young people. The review started by analysing the concept of adolescents, the global trend of unsafe sexual behaviours

among young people, followed by the global trend of STIs/HIV, chlamydia, teenage pregnancies, factors linked with unsafe sexual behaviours, and the global trend of various strategies against STIs among adolescents.
