The Health Literacy Questionnaire (HLQ) was developed as a comprehensive measure of health literacy, incorporating perspectives from the general population, patients, practitioners, and policymakers. The HLQ was created through a validity-driven approach, involving consultations, workshops, and interviews to identify distinct domains of health literacy. A total of 91 items were initially generated across 6 scales, but after psychometric analysis and refinement, 44 items were retained across 9 scales. These scales were validated using confirmatory factor analysis (CFA) and item response theory, with a 9-factor CFA model showing satisfactory fit: χ²(WLSMV)(866 d.f.) = 2927, p<0.000, CFI = 0.936, TLI = 0.930, RMSEA = 0.076, and WRMR = 1.698. The final scales included: Feeling understood and supported by healthcare providers; Having sufficient information to manage my health; Actively managing my health; Social support for health; Appraisal of health information; Ability to actively engage with healthcare providers; Navigating the healthcare system; Ability to find good health information; and Understanding health information well enough to know what to do. The HLQ covers nine conceptually distinct areas of health literacy, allowing for the assessment of needs and challenges across a wide range of individuals and organizations. It is designed to be useful in surveys, intervention evaluation, and studies of the needs and capabilities of individuals. The HLQ was developed using a grounded approach, incorporating concept mapping and patient interviews to derive the Health Literacy Management Scale (HeLMS). However, the HeLMS was found to have limitations, leading to the development of the HLQ. The HLQ was validated using a calibration sample (N=634) and a replication sample (N=405), with items refined to ensure clarity and psychometric validity. The HLQ provides a comprehensive assessment of health literacy, capturing a wide range of health literacy needs and capabilities. It is expected to be a useful tool in various settings, including health promotion, public health, and clinical interventions. The HLQ is also expected to provide insights into the mechanisms by which individuals can understand, access, and use health information and services, potentially serving as an operationalisation of empowerment in health. The HLQ is a robust and valid measure of health literacy, with strong psychometric properties and unique insights across nine separate areas. It is expected to be a suitable tool in many Western and Eastern cultures, although further studies are needed to confirm its applicability in each setting.The Health Literacy Questionnaire (HLQ) was developed as a comprehensive measure of health literacy, incorporating perspectives from the general population, patients, practitioners, and policymakers. The HLQ was created through a validity-driven approach, involving consultations, workshops, and interviews to identify distinct domains of health literacy. A total of 91 items were initially generated across 6 scales, but after psychometric analysis and refinement, 44 items were retained across 9 scales. These scales were validated using confirmatory factor analysis (CFA) and item response theory, with a 9-factor CFA model showing satisfactory fit: χ²(WLSMV)(866 d.f.) = 2927, p<0.000, CFI = 0.936, TLI = 0.930, RMSEA = 0.076, and WRMR = 1.698. The final scales included: Feeling understood and supported by healthcare providers; Having sufficient information to manage my health; Actively managing my health; Social support for health; Appraisal of health information; Ability to actively engage with healthcare providers; Navigating the healthcare system; Ability to find good health information; and Understanding health information well enough to know what to do. The HLQ covers nine conceptually distinct areas of health literacy, allowing for the assessment of needs and challenges across a wide range of individuals and organizations. It is designed to be useful in surveys, intervention evaluation, and studies of the needs and capabilities of individuals. The HLQ was developed using a grounded approach, incorporating concept mapping and patient interviews to derive the Health Literacy Management Scale (HeLMS). However, the HeLMS was found to have limitations, leading to the development of the HLQ. The HLQ was validated using a calibration sample (N=634) and a replication sample (N=405), with items refined to ensure clarity and psychometric validity. The HLQ provides a comprehensive assessment of health literacy, capturing a wide range of health literacy needs and capabilities. It is expected to be a useful tool in various settings, including health promotion, public health, and clinical interventions. The HLQ is also expected to provide insights into the mechanisms by which individuals can understand, access, and use health information and services, potentially serving as an operationalisation of empowerment in health. The HLQ is a robust and valid measure of health literacy, with strong psychometric properties and unique insights across nine separate areas. It is expected to be a suitable tool in many Western and Eastern cultures, although further studies are needed to confirm its applicability in each setting.