Loneliness represents a serious health risk. However, studies investigating social inequalities in loneliness are rare. Thus, the current study investigates which socioeconomic groups are the most affected by loneliness. Data from the population-based German Aging Survey were used (N = 3,784), with participants being 40+ years old. Education, income, and occupational prestige were used as socioeconomic indicators. It was found that loneliness scores were descriptively higher in groups with lower educational attainment, lower income and lower occupational prestige. In a linear regression analysis, significant socioeconomic differences in loneliness emerged only for income and occupational prestige. Thus, individuals with a low occupational position and those with low income are systematically more affected by loneliness than higher status groups. Material and occupational resources are likely to constitute major socio-structural explanatory variables for loneliness and should be further investigated as such by future studies.