Medical students have been shown to be vulnerable to mental stress. Strengthening individual protective characteristics can be one cornerstone for promoting medical students' mental health and thereby preventing mental disorders. Online programs are an opportunity to provide appropriate options that have the advantage of being accessible from anywhere, at any time, and with a low entry threshold. This review provides a literature overview of current online programs for medical students. The findings can serve as a point of reference for designing effective online programs for mental health-promotion and mental disorder-prevention in medical curricula. We applied a systematic literature search in PubMed, ERIC, Cochrane, and Web of Science. Programs offered had to be web-based, and the addressed group had to be medical students. Protective individual characteristics for mental health and information on the programs' effectiveness were included in the search. As outcomes, we included mental health, burnout, symptoms of depression, anxiety, and well-being. The search yielded 723 articles; of them, 11 met the inclusion criteria. Programs found were grouped according to their focus: mental health literacy, mindfulness, based on Cognitive Behavioral Therapy, or peer support. Two studies showed significant reductions in perceived stress; one study indicated reduced burnout levels. One program had significant immediate effects on mindfulness, empathy, and resilience; two studies indicated strengthening coping strategies. Two programs were qualitatively assessed as helpful; two studies are ongoing. Nine studies lacked control groups; two randomized controlled trials were ongoing. Only a few online programs with limited evidence of effectiveness were found. They addressed protective individual characteristics, highlighting their importance for mental health. Thus, more health-promoting and mental disorder-preventing programs with high-quality effectiveness studies are necessary. An integration of such programs into curricula would allow for greater utilization and could give greater emphasis to and prioritize mental health in medical education.