Loneliness and the need to belong are two subjective states that, on the basis of prior research and theory, would appear to be related both to one another and to wellbeing. This study explored these relationships with a sample of 436 volunteer participants drawn from the Australian Unity Wellbeing database. Participants completed a survey that included a measure of satisfaction with personal relationships embedded in the Personal Wellbeing Index, the UCLA Loneliness scale, a measure of life satisfaction, and the Need to Belong Scale. While loneliness was weakly related to need to belong, it was strongly associated with the discrepancy between need to belong and satisfaction with personal relationships, which we used to measure unmet need for belonging. People living alone reported a lower need to belong and less satisfaction with personal relationships than those living with others. However, the discrepancy scores, life satisfaction scores and loneliness scores did not differ between these groups. Loneliness mediated the relationship between unmet need for belonging and wellbeing (life satisfaction). These findings support Baumeister and Leary’s “belongingness hypothesis” and clarify the relationship between these variables.