As global and national pursuit of universal health coverage (UHC) accelerates, health system quality has emerged as a critical concern, a weakness that could blunt the promise of UHC. Without adequate quality of care, access to care and financial protection will be insufficient to improve population health. Findings from the recent Lancet Global Health Commission for High Quality Health Systems suggest that increasing the scope and reach of health systems without attention to improving quality has the potential to worsen health [1]: individuals can be harmed by unsafe procedures or unnecessary treatment, communities may lose faith in health systems, and already limited resources will be misdirected. Health systems in low- and middle-income countries (LMICs) today demonstrate broad and deep gaps in readiness to provide care [2–5], systematic deficiencies in diagnosis and treatment [6–8], and frequent reports of disrespectful care [9]. As of 2016, receipt of poor-quality care resulted in an estimated 5 million excess deaths in LMICs [10]. The breadth of this quality deficit—spanning long-standing global health priorities such as maternal [11] and child health [4], as well as understudied needs such as mental healthcare [12]—demands a new generation of research to compel change.