Purpose <p>Gaslighting is an increasingly recognized and studied form of psychological abuse in intimate partner violence (IPV) that targets an individual’s trust in their own knowing abilities. Development of a theoretically and methodologically rigorous measure of gaslighting in IPV is vital for further study and deeper understanding of this pervasive and harmful form of abuse. The present study sought to develop such a scale, the Gaslighting in Relationships Scale (GRS).</p> Methods <p>Item generation for the GRS was informed by literature review, subject-matter expert consultation, and research and clinical experiences with IPV survivors. Items were refined through cognitive interviews and qualitative data analysis. Study 1 included an exploratory factor analysis (EFA) of the GRS, using an online sample (<i>n</i> = 249), and study 2 included a confirmatory factor analysis (CFA) with a sample of survivor-mothers engaged in custody litigation (<i>n</i> = 222).</p> Results <p>Initial item generation resulted in nine items, one of which was removed based on the qualitative refinement process. The EFA conducted with the remaining eight items in study 1 resulted in a single factor structure, accounting for 48.43% of the total variance. The CFA in study 2 confirmed the acceptability and fit of the one-factor model.</p> Conclusions <p>The GRS will be valuable tool for identifying and assessing the presence of gaslighting in research, clinical, and other practice settings.</p>