Thomas Hobbes of Malmesbury (1588-1679) is one of the most influential British philosophers of the seventeenth century. The paper reconstructs Hobbes’s legal theory, focusing on his definition of law (civil law, as he calls it) found in Leviathan, XXVI, 3. The definition is only apparently simple, since it has been interpreted in different ways, especially with regard to the connections with natural law—and the Hobbesian assertion that civil law and natural law “contain each other”. Moreover, the definition of civil law changes in the corresponding paragraph of the Latin version of 1668. What is the meaning of this change? What about the divisions of the law/divisio legis, which—as Hobbes emphasizes—appears in different forms in different writers? Finally, if a good law is “that which is needful, for the good of the people”, what is it that dictates the paths to be followed by the sovereign representative, who is also the supreme legislator, when writing a new law? These are the main problems in Hobbes’s legal thought that the paper will address.