Although scientific research on adolescent romantic and sexual development has proliferated in recent years, currently, too little is known about how development in these areas can be understood across diverse populations (e.g., different socio-cultural groups within countries) and contexts (e.g., countries or different proximal social environments). The goal of the current virtual special issue in the Journal of Adolescence was to highlight relevant and timely empirical findings from studies utilizing innovative and diverse research methods in the areas of adolescent romantic and sexual development from around the globe, with an emphasis on data collected outside of the Western world. It combines an interesting set of nine empirical papers, which describe datasets from 5 countries (Canada, India, Indonesia, Mexico, and the United States). In this editorial, we provide an introduction to this special issue, and illustrate how these studies expand our understanding of adolescent romantic and sexual development by examining: 1) romantic and sexual relationship constructs that are relevant for understudied and diverse populations; 2) how culture-specific factors may shape adolescents' romantic and sexual relationships; 3) how romantic and sexual relationship constructs are linked to psychosocial adjustment outcomes in understudied cultural contexts; 4) the role of different proximal social environments (e.g., parents, siblings, peers) in romantic and sexual development in diverse populations. Copyright © 2020 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.