Background: European public healthcare systems are expanding eHealth tools such as teleconsultations, online appointment bookings, and electronic health records (EHRs) to improve efficiency and access to healthcare. However, their use depends on factors like digital skills and internet access, which are unequally distributed across socioeconomic and demographic determinants. Most existing evidence on these inequalities are qualitative or outside universal healthcare systems. Objective: This systematic review aims to synthesize quantitative evidence on inequalities in access to and use of eHealth services—such as online appointment booking, teleconsultations, and access to EHRs an eHealth portal—within European public healthcare systems, by examining differences across age, gender, socioeconomic status, education, and other social determinants of health. Methods: A systematic search was conducted across four electronic databases (PubMed, Scopus, Web of Science, and PsycINFO) for studies published in English or Spanish between 2015 and 2025. Eligible quantitative studies focused on adults aged 18 and older using public healthcare systems in European countries. Screening and data extraction were independently performed by three reviewers using Rayyan®, with disagreements resolved by a third reviewer. Extracted information included study characteristics, population details, digital health tools assessed, social determinants, and quantitative outcomes. Risk of bias was evaluated using Joanna Briggs Institute appraisal tools. Due to study heterogeneity in the digital tools assessed and inequality dimensions analyzed, a narrative synthesis was used to summarize findings by type of digital tool and social inequality factors. Results: A total of 2,366 records were retrieved through the initial search, from which 18 studies were included in the systematic review. Publication output increased notably from 2020 onwards, with most studies published between 2020 and 2025. Most of the research originated from northern and western Europe. The findings of this review reveal consistent social gradients in the use of digital health tools within European public healthcare systems. Older adults, individuals with lower educational or socioeconomic level, ethnic minorities, and those with limited digital skills or health status were less likely to use eHealth tools. Conclusions: Digital transformation in European public health systems has not benefited all groups equally. This review highlights persistent social inequalities in the use of key digital health tools. However, existing research has certain limitations, including heterogeneity in study designs and populations, exclusion of qualitative studies due to methodological criteria, and geographical concentration of studies primarily in Northern and Western Europe. Future research should deepen understanding of how these inequalities emerge and interact, incorporating both individual and structural factors. Emphasizing an intersectional approach and standardizing measures of digital access will be essential to develop effective, equity-focused policies that ensure inclusive digital health services for all. Clinical Trial: PROSPERO CRD420251015756;https://www.crd.york.ac.uk/PROSPERO/view/CRD420251015756.