Thomas Hobbes's Leviathan is one of the most important philosophical texts in the English language, and one of the most influential works of political philosophy ever written. This is the first critical edition based on a full study of the manuscript and printing history. It is also the first edition to place the English text side by side with Hobbes's later Latin version of it, complete with a set of notes in which the many passages that differ in the Latin are translated into English. So, for the first time, readers of Leviathan will be able to see clearly every stage of the development of the text. Both texts are fully annotated with explanatory notes. The editor's Introduction, which takes up the whole of the first volume, gives a path-breaking account of the work's context, sources, and textual history. This definitive edition will set the study of Hobbes's masterwork on a new basis.