Significant efforts are underway across the globe to strengthen gender data capacity and use. However, without a sound understanding of where investments in gender data are most needed, how effective they are, and how they translate into meaningful action for gender equality, their impact is limited. This paper, jointly produced by UN Women and PARIS21 (under the Women Count Phase II programme) provides an in-depth review of existing indicators on gender data capacity and use. Based on the results of the review, the paper puts forward a comprehensive new framework for understanding gender data capacity, which aims to provide a tool for assessing the maturity of statistical systems in terms of how they produce, use and disseminate gender data, and how these data are taken up outside national statistical systems.