Our study analyses the reasons for the gender gap in academic entrepreneurship among UK-based academics from across a wide range of academic disciplines. We focus on spinout activity as a measure of academic entrepreneurship, and explore the relevance of the different explanations for the gender gap. Our analysis is based on a unique survey of UK academics conducted over 2008/2009. The survey provides micro-data on over 22,000 academics in the sciences, social sciences, arts and humanities, across all higher education institutions in the UK. Our results show that female academics differ from the male academics in the sample in important ways. Female academics are more likely to be involved in applied research, to hold more junior positions, to work in the health sciences, social sciences, humanities and education, to have less prior experience of running a business, and to feel more ambivalent about research commercialisation. All of these characteristics are correlated with lower rates of spinout activity. Using a non-parametric decomposition analysis, we show that certain combinations of characteristics of male academics have few or no matches to female academics, and these characteristics explain a large proportion of the gender gap.