In preparation for the peace conference that was expected to follow World War I, in the spring of 1917 the British Foreign Office established a special section responsible for preparing background information for use by British delegates to the conference. International Rivers is Number 149 in a series of more than 160 studies produced by the section, most of which were published after the conclusion of the 1919 Paris Peace Conference. The study was written by Belgian legal scholar Georges Kaeckenbeeck (1892–1973) and thus is one of relatively few in the series issued under the name of an individual author. Kaeckenbeeck distinguishes between a national river lying wholly within the territory of one state and subject to its jurisdiction, and an international river, defined as a “river navigable from the sea, which flows through or along the territory of two or more States.” International rivers are subject to the jurisdiction of more than one state and may be subject to principles or provisions of international law affecting the river as a whole. Part one covers general legal theories and principles, including those associated with or derived from feudalism, Roman law, the law of nature, and other sources. Part two deals with the laws relating to international rivers growing out of the Congress of Vienna (1814−15) and their application to the Rhine, Scheldt, Elbe, Weser, and other European rivers. This section also covers the legal regime governing navigation on the Danube River, which was established in the second half of the 19th century, but which generally followed the precedents set at the Congress of Vienna. Also discussed are the arrangements made by the European powers at the Conference of Berlin (1884−85) regarding navigation on the Congo and Niger Rivers. The final section draws general conclusions, summarizes the attitudes of the major powers regarding international riparian law, and discusses standard provisions contained in agreements relating to international rivers. The appendices include the texts of important international agreements and a brief summary of international legal issues relating to North American rivers, notably the Mississippi and Saint Lawrence, and to the Amazon and other South American rivers.