An increasing number of fora and networks have been recognised to play a role in international or transnational normative processes. While lawmaking by formal, intergovernmental international organizations received abundant attention over the past years, we know less about a phenomenon that this paper refers to as ‘informal international lawmaking’ (IN-LAW). Lawyers struggle with the new and extensive normative output in global governance. We nevertheless use the term ‘law’ to connote the exercise of public authority, as opposed to what is often referred to more broadly as ‘regulation’ (covering both public and private regulation). IN-LAW, as we define it, can include private actor participation, but excludes cooperation that only involves private actors. The present paper thus purports to introduce the concept of ‘informal international lawmaking’ and it will present some findings based on case studies in the IN-LAW project related to the reasons for actors to opt for informal lawmaking. We also analyse whether − and to what extent ‒ IN-LAW bodies are subject to some form of accountability and, if so, in what form and at what level. Finally, we will look at some consequences of informal international lawmaking, in particular in relation to the changing role of law in global governance.