BACKGROUND: Worldwide, approximately 800,000 persons die by suicide every year; with rates of suicide attempts estimated to be much higher. Suicidal persons often suffer from a mental disorder but stigma, lack of available and suitable support, and insufficient information on mental health limit help seeking. The use of internet-based applications can help individuals inform themselves about mental disorders, assess the extent of their own concerns, find local treatment options, and prepare for contact with health care professionals. This project aims to develop and evaluate e-mental health interventions to improve knowledge about suicidality and to reduce stigmatization of those affected. In developing these interventions, a representative telephone survey was conducted to detect knowledge gaps and stigmatizing attitudes in the general population. METHODS: First, a national representative telephone survey with N = 2000 participants in Germany was conducted. Second, e-mental health interventions are developed to address knowledge gaps and public stigma detected in the survey. These comprise an evidence-based health information package about suicidality, information on regional support services, a self-administered depression test-including suicidality-and an interactive online intervention including personal stories. The development is based on a trialogical exchange of experience between persons affected by suicidality, relatives of affected persons, and clinical experts. Australian researchers who developed an e-mental health intervention for individuals affected by rural suicide were invited to a workshop in order to contribute their knowledge and expertise. Third, the online intervention will be evaluated by a mixed methods design. DISCUSSION: From representative telephone survey data, content can be developed to address specific attitudes and knowledge via the e-mental health interventions. These interventions will be easily accessed and provide an opportunity to reach people who tend not to seek professional services, prefer to inform themselves in advance and/or wish to remain anonymous. Evaluation of the online intervention will provide information on any changes in participants' self-stigma and perceived-stigma of suicidality, and any increase in participants' knowledge on suicidality or self-efficacy expectations. TRIAL REGISTRATION: German Clinical Trial Register DRKS00015071 on August 6, 2018.