This concise textbook provides a broad picture of the basic rules governing the legal organisation and functioning of the international society of states. Namely, its subjects, sources, the consequences of breaches of the law, dispute settlement, and its relation to domestic jurisdictions. A broad-brush illustration is also given of key bodies of substantive international law, with special regard to the law of the sea, environmental law, human rights law, investment and trade law, international criminal law, jurisdictional immunities, and migration law. The slim format of the book purports to complement by way of introduction the specific syllabus which may be chosen by teachers. It is also meant to embolden domestic attorneys to realise the entanglement between international law and many of the legal rules they interpret and apply on a daily basis. Method wise, international law is presented here following no particular doctrinal approach, but according to the way international law is pleaded before and applied by international and domestic courts and tribunals.