Interpersonal emotion regulation occurs when people try to manage their own or others' feelings or emotional expressions via social interactions. Research on this distinctive form of emotion regulation has grown exponentially over the last 15 years. In this article, we draw from literature across different disciplines, including multiple subdisciplines within psychology (e.g., social, clinical, developmental, organizational, sports), neuroscience, and sociology, to reflect on what is currently known about interpersonal emotion regulation. Our analysis focuses on the process through which interpersonal emotion regulation unfolds, its outcomes, and the development of abilities and difficulties in interpersonal emotion regulation through the lifespan. We also introduce this special issue, which presents a collection of 17 articles that advance our knowledge about these aspects of interpersonal emotion regulation in multiple ways. Finally, we chart the path forward by considering some of the most important challenges and opportunities for researchers aiming to deepen our understanding of interpersonal emotion regulation. (PsycInfo Database Record (c) 2025 APA, all rights reserved).