User engagement is critical to the success of digital health interventions. Despite its importance, many interventions fail to engage users effectively. Understanding the dynamics of engagement remains a complex task. This umbrella review presents a comprehensive and up-to-date summary of the key findings on user engagement with technology. A total of 65 reviews published between 2011 and 2023 were identified from PubMed, Scopus, and ScienceDirect databases. This review explores the factors that impact user engagement (e.g., design features, design processes, system characteristics, intervention characteristics, and user characteristics) and user engagement strategies (i.e., personalization and gamification). The relationship between user engagement and health outcomes has shown mixed results. We synthesized the essential gaps and recommendations regarding user engagement from the reviews. Critical avenues for future research such as co-design methods and standardized measurements were outlined.