IntroductionGenito-pelvic pain/penetration disorder (GPPPD) not only adversely affects women’s sexuality and sexual satisfaction but is also associated with a wide range of psychosocial consequences such as reduced quality of life and well-being, mental health comorbidities, and relationship distress. Evidence for effective treatment options is scarce.AimThis article describes the rationale, treatment protocol, and study design for a randomized controlled trial examining the efficacy of an Internet-based guided intervention for GPPPD.MethodTwo hundred women who meet the criteria for GPPPD and have not been able to experience sexual intercourse for at least the last 6 months will be recruited and randomly assigned either to the intervention group (IG) or a 6-month waitlist control group. Assessments take place at baseline (T1), peritreatment after completion of Session 5 in IG (T2), after completion of Session 8 or 12 weeks after randomization (T3), and after 6 months (T4). Data will be analyzed on an intention-to-treat and a completer basis.Main outcome measuresThe primary outcome will be sexual intercourse involving the insertion of the partner’s penis at posttreatment. Secondary outcomes include, e.g., improved non-intercourse penetration, sexual functioning, dyadic stress coping, reduced fear of sexuality and negative penetration-related cognitions. Fear of sexuality, penetration-related cognitions, and exercise intensity will be assessed as mediators of intercourse in the IG. Sexual dysfunctions of partners will be measured at baseline (T1) and investigated as a potential moderator of the primary treatment outcome.DiscussionGiven the burden associated with GPPPD and the need for specialized treatment, there is a surprising lack of evidence-based treatment options. This study aims to assess whether Internet-based interventions could contribute to closing this treatment gap.Clinical Trial RegistrationGerman Register of Clinical Studies (DRKS): DRKS00010228.