Tackling gender inequality is a key focus for both civil society and government policy in Great Britain (GB). Yet, there is currently no consensus on how to conceptualize or operationalize gender inequalities, nor any detailed measurement of gender inequalities at the sub-national level, despite high levels of regional inequality. This is a barrier to the development and evaluation of gender equality programs and policies, and to holding the government accountable. To address this gap, we propose a framework for a sub-national index of gender inequalities in GB based on a review of relevant indices, theoretical models and policy. This framework was further developed in a workshop with stakeholders. We also scope the data currently available from survey and administrative sources to capture the proposed framework, highlighting gaps in our ability to comprehensively measure gender inequalities at the sub-national level in GB.