A systematic review of 116 studies across 42 countries reveals that only 50 validated instruments exist to measure autonomy among adults over 60, despite involving nearly one million participants. The research evaluated these tools using COSMIN methodology standards for structural validity, reliability, and cross-cultural applicability. This scarcity represents a critical measurement gap in geriatric care, where autonomy—the capacity for self-determination in daily decisions—increasingly defines successful aging outcomes. The limited toolkit constrains both clinical practice and policy development, as healthcare systems struggle to quantify what many consider the cornerstone of person-centered elder care. Most existing instruments likely focus on physical independence rather than broader psychological and social dimensions of autonomy. This methodological blind spot becomes increasingly problematic as populations age globally and healthcare shifts toward preserving agency rather than merely extending survival. The review's international scope underscores how this measurement deficit transcends individual healthcare systems, suggesting that fundamental concepts of aging well remain poorly operationalized across cultures. Without robust autonomy metrics, clinicians cannot adequately assess interventions designed to maintain older adults' self-direction, and policymakers lack data to design age-friendly environments that preserve human agency.