<p>Research on social connection has proliferated across psychology over the past two decades, with rapid growth in the past 10–15 years. However, this broad interest has led to ‘social connection’ becoming a catch-all term, such that disparate strands of work are based on different approaches to conceptualization and measurement. In this Review, we synthesize prior research and highlight four distinct uses of the term ‘social connection’ — as subjective perceptions, social networks, interpersonal&#xa0;synchrony and interpersonal behaviours — and describe how research based in each conceptualization has contributed to understanding of&#xa0;the concept. We also review how constant connectivity via smartphones and social media has changed and challenged the landscape of social connection research. We conclude by highlighting the complex links between the different conceptualizations of social connection (and constant connectivity) and discuss how fragmentation poses challenges to scientific progress and public communication. By categorizing and clarifying subsets of the literature, we aim to facilitate communication across areas of psychological science and thereby guide research towards a more holistic understanding of social connection.</p>