Objectives. We developed the Ethnic-Racial Discrimination Stress Inventory (ERDSI), a 27-item culturally-relevant and comprehensive measure, to assess subjective experiences of ethnic-racial discrimination stress in Mexican-origin people in the United States and Turkish-origin people in Germany, two groups who share similar sociocultural characteristics and immigration experiences.Methods. We developed 73 items to capture firsthand, intragroup, and vicarious discrimination, and internalization and expectations of discrimination. Adults of Mexican origin in the U.S. (N = 258) and of Turkish origin in Germany (N = 106) completed an online survey of these items, measures of related constructs, and sociodemographic measures. Results. Study 1: We eliminated items based on inter-item correlations and their performance in exploratory factor analyses (EFA) in the U.S.-based Mexican sample. The EFA resulted in a four-factor, 27-item solution (F1: Vicarious Discrimination Stress, seven items; F2: Internalization of Discrimination Stresses, seven items; F3: Firsthand Discrimination Stress, seven items; and F4: Intragroup Discrimination Stress, six items). The ERDSI factors were reliable and demonstrated convergent and criterion-related validity. The factors predicted well-being measures after adjustment for control variables and COVID-19-related stressors, demonstrating incremental validity. Study 2: We conducted reliability and validity analyses of the three ERDSI factors (F1, F2, F3, not F4) that applied to the German-based Turkish sample. These three factors demonstrated reliability and convergent, criterion-related, and incremental validity. Conclusions. The ERDSI is a psychometrically sound measure of racial-ethnic discrimination stress and can be used in studies with people of Mexican origin in the U.S. and people of Turkish origin in Germany. Key words: ethnic-racial discrimination, internalization, stress, ethnic minority, cross-cultural