OBJECTIVES: To clarify the factors associated with loneliness in individuals aged 80 years and older in Germany (also stratified by sex). METHODS: Data from the nationally representative "Old Age in Germany (D80+)" were employed. The analytic sample equaled 10,031 individuals. The D80+ study included community-dwelling and institutionalized individuals ≥ 80 years in Germany. Multiple linear regressions were used (with sociodemographic and health-related explanatory factors). The collection of data occurred between November 2020 and April 2021 (written questionnaire). RESULTS: Higher loneliness was significantly associated with not being married (e.g., widowed compared to being married, β=0.37, p<.001), being institutionalized (β=0.33, p<.001), low education (high education compared to low education, β=-0.07, p<.01), a higher number of chronic conditions (β=0.02, p<.001), poor self-rated health (β=-0.19, p<.001) and greater functional impairment (β=0.15, p<.001). Sex-stratified regressions produced comparable results. However, low education was only associated with higher loneliness among men, but not women (with significant interaction: education x sex). CONCLUSION: Several sociodemographic and health-related factors can contribute to loneliness among the oldest old in Germany, with sex-specific associations between education and loneliness. Overall, such knowledge can aid to address individuals with higher loneliness levels.