Youth sexuality has been primarily studied with a focus on its potential public health issues, such as sexually transmitted infections and unwanted pregnancies, and its comorbidity with other risky behaviors. More recently, it has been studied as a normative step in romantic partnerships, either pre- or post-marital, as well as outside the context of romantic involvement. In this paper, we review the extensive literature on sexuality in adolescence and early adulthood both within and outside romantic relationships (i.e., casual sexual relationships and experiences; CSREs). Furthermore, the recent recognition of youth sexuality as a developmental task has led to a renewed interest from scholars in youth who abstain from sexual encounters, whether deliberately or not. A brief overview of the literature on cultural differences in sexuality, and sexual-minority youth sexual development is also provided. This paper concludes by suggesting future directions to bring the field of youth sexuality and romantic relationships forward.