<p>The relationship between social media use and loneliness among adolescents is a growing area of research, with mixed findings on whether social media use is associated with increased (displacement hypothesis) or decreased (stimulation hypothesis) loneliness. So far, the relationship between social media use and loneliness by online interaction partner or age has hardly been investigated. Therefore, this study explores the associations between social media communication with different persons and loneliness. Furthermore, the link between problematic social media use and loneliness, as well as age differences, were analyzed. Data from the representative 2022 German Health Behavior in School-aged Children (HBSC) survey, including 6,475 students aged 11, 13, and 15&#xa0;years (girls: 50,6%, <i>M</i>_<i>age</i> = 13,4, <i>SD</i> = 1,7), were used. Loneliness was measured via the University of California–Los Angeles Scale (UCLA). Chi-square tests and regression analyses were conducted. In total, 11.8% of the children were classified as lonely, with girls and gender-diverse individuals showing higher levels of loneliness than boys. High levels of contact with close friends via social media were linked to lower levels of loneliness, whereas interaction with internet friends was associated with greater levels of loneliness. A total of 11.1% of students reported problematic social media use, which was associated with a higher likelihood of feeling lonely. The relationship was not moderated by age. These findings support both the displacement and stimulation hypotheses, suggesting that the role of social media depends on how and with whom it is used. Interacting with close friends on social media is linked with lower levels of loneliness, whereas problematic use and online-only interactions are associated with higher levels of loneliness, regardless of age. Thus, interventions should focus on promoting healthy social media habits and encouraging meaningful connections with close friends.</p>