Project Summary/Abstract Transgender adults in the U.S. are disproportionately affected by tobacco use. Transgender adults are more than twice as likely to smoke cigarettes than the general U.S. adult population. In addition to the great burden of disease tobacco use places onto this population, tobacco use is also a contraindication for gender-affirming care, a medical necessity for many transgender persons to achieve full mental and physical health. Despite the health-related needs of transgender adults, existing smoking cessation interventions fail to address the specific needs of this population. As such, the National Academy of Medicine and U.S. Surgeon General identifies transgender-specific health needs and developing and testing the effectiveness of interventions for transgender adults a national priority. Despite the role health care providers can play in cessation, transgender adults report barriers to accessing evidence-based, clinician-delivered interventions. A transgender-specific mHealth intervention could serve as a cost-effective and scalable solutions to improving health outcomes for this often hard-to-reach population. Furthermore, such an intervention can be a health services resource for health care providers who might not have the time or expertise to provide gender affirming smoking cessation support to their transgender patients. Building on our team's research expertise in transgender health, mHealth, tobacco cessation, and health systems tobacco-related care, we propose to develop and pilot test an mHealth smoking cessation intervention for transgender adults: Proud to Quit (P2Q). P2Q will provide tailored messages, peer social support, and self-monitoring features. We will develop P2Q by collaborating with an Intervention Advisory Workgroup comprising of transgender adults and providers of gender affirming health care, and implement iterative intervention design processes and usability testing. Through a remote pilot randomized controlled trial, we will assess acceptability and feasibility of an mHealth smoking-cessation intervention for transgender adults as well as its preliminary efficacy using self-report and objective biomarker data. The findings from this proposal will inform the feasibility of and protocols for a full-scale services research effectiveness trial. The project would redress the dearth of smoking-cessation interventions tailored to transgender adults by offering a new tool and the ability to reach transgender adults in diverse locations; it would offer a cost-effective approach that ensures the intervention can be broadly disseminated with fidelity; and, ultimately, it would reduce tobacco-related health disparities among transgender adults, who are disproportionately affected by tobacco use.