Background: Over the last decade, increasing evidence from worldwide has shown that the prevalence of avoidance, social withdrawal, and loneliness (ASWL) has increased substantially and has become a major public health issue, not only among elderlies but also among teens and young adults. Despite the importance of the topic, there is a dearth of published research on the subject in Arab and developing countries (such as Oman). Aim: This thesis aims to study social isolation and loneliness among university students, their risk factors, and their associations with mental health and selected sociodemographic and academic characteristics. Methods: A cross-sectional study was conducted over an eight-weeks period, from 01 February to 31 March 2023. The total number of participants was 200 students from Sultan Qaboos University (SQU) with a response rate of 85%. A self-reported questionnaire was designed to collect the data required for the study. The questionnaire included sociodemographic and academic characteristics as well as sections covering the following standard survey tools: Loneliness Scale UCLA-7, Lubben Social Network Scale (LSNS6), and Depression, Anxiety and Stress Scale (DASS-21). Results: Overall, there were a total of 170 participants, of whom 69 (40.6%) reported an LSNS-6 score consistent with social isolation (social isolation group, SIG) while the remaining 101 (59.4%) reported LSNS-6 scores that showed that they were not socially isolated (non-social isolation group, non-SIG). The adjusted odds ratios (OR) reported from the multivariate logistic regression modeling indicated that having social isolation was associated with several risk factors; however, the associations were statistically nonsignificant (P> 0.05). The strongest association was associated with having no children (OR= 1.99; 95%CI 0.38, 10.33), followed by never being married (OR= 1.68; 0.47, 5.99). Compared to non-SIG, the adjusted ORs indicated that being socially isolated was vi significantly associated with an increased risk of having psychological disturbances. The highest risk was associated with anxiety (OR= 23.16; 95%CI 3.06, 175.48; P= 0.002), followed by depression (OR= 6.53; 95%CI 2.09, 20.41; P= 0.001), and then stress (OR= 5.07, 95%CI 2.26, 11.40; P= 0.001). The differences between SIG and non-SIG students were statistically significant across all levels of severity of all psychological disturbances (P0.001). The means of Loneliness scale (UCLA-7) category-scores were higher among the SIG students than non-SIG students. Conclusion: The study findings suggest that social isolation is a common experience among university students and affects all types of students irrespective of their background or academic performance. The study found that social isolation was associated with poor mental health outcomes among university students. The study calls for universities to take steps to address social isolation among their students to promote their mental health and well-being. Universities may implement various interventions, including social support programs, mental health services, and peer mentorship programs, to enhance students' social connectedness and mitigate the negative consequences of social isolation on their academic and personal well-being