Much has been written about policy efforts to achieve 'Health in All Policies' an ambitious attempt to improve population health and reduce health inequalities by ensuring multiple policy areas are more attuned to their health impacts. However, most accounts focus on technical challenges, such as implementing impact assessments. In contrast, and focusing on the European Union, this book argues that 'Health in All Policies' is essentially a political project shaped by institutional power, competing ideas, and discourses. We can only really understand the failure to realise its ambition through political analysis.