Loneliness is a common experience with major negative consequences for well-being. Although much research has examined protective and risk factors for loneliness, we know little about its cultural underpinnings. The few studies that exist seem paradoxical, suggesting that loneliness is higher in cultures where tighter and more demanding (i.e., more restrictive) cultural norms about social relationships decrease the risk of social isolation. At the same time, loneliness is lower among individuals who hold more restrictive norms or perceive such norms among others around them. We move beyond previous research by generating the culture-loneliness framework, suggesting that loneliness occurs across all levels of restrictiveness, but through different predominant types of isolation. More restrictive (i.e., more, tighter, or more demanding) norms about social relationships may better protect from physical isolation (i.e., a lack of social interaction or relationships) but increase the likelihood of emotional and perceived isolation (i.e., a lack of individually satisfying relationships or relationships that do not fulfill cultural ideals). We evaluate this framework by reviewing research at both the individual and the cultural levels, and discuss its theoretical and practical implications.