It is unusual to discuss ‘compulsory licences’ and the activities of collecting societies in the context of the public domain, but various forms of compulsory licensing now constitute some of the public domain’s most important components in many countries. This seems likely to increase, with much scope for more countries to use the various forms of compulsory licences within the tolerances of international copyright law, in order to achieve net social benefits. To be part of the public domain, ‘compulsory licences’ are where rights holders are required to allow their works to be used by parties specified by the licence terms, on conditions and for a fee set by a neutral party on public interest grounds, and on equal terms for licensees. In other words, rights holders are compelled to allow what would otherwise be copyright infringements in return for remuneration. We distinguish ‘statutory licences’, created and made mandatory by statutory provisions, from extended collective licences (ECLs), and analyse the main features of each. Their positions under international and EU law, and implementation in countries as diverse as the UK, United States, Australia, Nordic countries, China and India, are considered. Chapter 14 considers the main subject areas of compulsory licences.