Major depressive disorder is a common mental health condition that affects an estimated 16.2 million adults and 3.1 million adolescents in the United States. Yet, a lack of uniformity remains in measurements and monitoring for depression both in clinical practice and in research settings. This project aimed to develop a minimum set of standardized outcome measures relevant to both patients and clinicians that can be collected in depression registries and clinical practice. Twenty-nine depression registries and related data collection efforts were identified and invited to submit outcome measures. Additional measures were identified through literature searches and reviews of quality measures. A multistakeholder panel representing clinicians; payers; government agencies; industry; and medical specialty, health care quality, and patient advocacy organizations categorized the 27 identified measures using the Agency for Healthcare Research and Quality’s supported Outcome Measures Framework. The panel identified 10 broadly relevant measures and harmonized definitions for these measures through in-person and virtual meetings. The harmonized measures represent a minimum set of outcomes that are relevant to clinicians and patients and appropriate for use in depression research and clinical practice. Routine and consistent collection of these measures in registries and other systems would support creation of a national research infrastructure to efficiently address new questions, improve patient management and outcomes, and facilitate care coordination.