AbstractBackgroundLoneliness is a growing public health concern, yet little is known about loneliness in young people. The current study aimed to identify social ecological factors related to loneliness and examine the extent to which geographic region may account for differences in loneliness.MethodsThe data come from a cross-sectional sample of 6503 young people living in the UK. Loneliness was measured using the UCLA 3-item scale. Bivariate analyses were used to test associations between each predictor and loneliness. Multilevel models were used to identify key social ecological factors related to loneliness, and the extent to which loneliness may vary across geographic regions (local authority districts).ResultsSociodemographic, social, health and well-being, and community factors were found to be associated with loneliness. Geographic region was associated with 5–8% of the variation in loneliness. The effect of gender, sexual orientation and minority ethnic background on loneliness differed across regions.ConclusionsThis is the first study to highlight modifiable social and community factors related to youth loneliness, and individual vulnerabilities, such as poor mental well-being. Results related to geographic differences suggest that local-level initiatives may be most appropriate in tackling loneliness, rather than wider, less contextualized national efforts.