Current efforts to address and alleviate the suffering and harms associated with gambling disorder (GD) predominately involve in-person psychotherapy or static web-based interventions, while dynamic, proactive approaches to the treatment of GD are needed. Currently, several mHealth apps for GD exist, but none are empirically validated and, even though they could be potentially useful, these interventions are static, reactive approaches and they are not based on the geofencing principle. Advances in smartphone technology now allow for a paradigm shift. Just-in-time adaptive interventions (JITAI) are technology-based dynamic interventions that proactively respond to time-varying information to provide intervention at critical moments. In this paper, we present a novel JITAI mHealth app for GD called "Don't Go There'' (DGT).