A strong organisational cybersecurity culture (CSC) is critical to the success of any cybersecurity effort, and understanding and measuring CSC is essential if it is to succeed. To facilitate the framing and measurement of CSC we conducted a rapid evidence assessment (REA) to synthesise relevant studies on CSC. The systematic search identified 1,768 records. 52 studies were eligible for the final synthesis. Content analysis of the CSC definitions in the eligible studies highlighted that CSC should not be viewed solely as a technical problem but as a management issue too; CSC requires top management involvement and role modelling, with full organisational support for the desired employee behaviours. We identify both theoretically and empirically derived models of CSC in the REA, along with a range of methods to develop and test these models. Integrative analysis of these models provides detailed information about CSC dimensions, including employee attitudes towards CS; compliance with policies; the role of security education, training and awareness; monitoring of behaviour and top management commitment. The evidence indicates that CSC should be understood both in the context of the wider organisational culture as well as in the shared employee understanding of CS that leads to behaviour. Based on the findings of this review, we propose a novel integrated framework of CSC, consisting of cultural values; the culture-to-behaviour link and behaviour itself. We also make measurement recommendations based on this CSC framework, ranging from simple, broad-brush tools through to suggestions for multi-dimensional measures, which can be applied in a variety of sectors and organisations.