The commitment to ‘leave no one behind’ has been a key feature of all the discussions on the post-2015 agenda and the Sustainable Development Goals (SDGs). The idea that ‘no goal should be met unless it is met for everyone’ is well established in the rhetoric around the new goals. In theory of course, this means ensuring that every individual achieves the full package of rights and opportunities the SDGs express. However, what this means in practice is still not clear. This briefing looks at how the idea of leaving no one behind can be integrated into the SDGs.