The Laws (Ancient Greek: Νόμοι) is Plato's last and longest dialogue. The conversation depicted in the work's twelve books begins with the question of who is given the credit for establishing a civilization's laws. Its musings on the ethics of government and law have frequently been compared to Plato's more widely read Republic. Some scholars see this as the work of Plato as an older man having failed in his effort to guide the rule of the tyrant Dionysius II of Syracuse. These events are alluded to in the Seventh Letter. The text is noteworthy as the only Platonic dialogue not to feature Socrates.

Unlike most of Plato's dialogues, Socrates does not appear in the Laws. The conversation is instead led by an Athenian Stranger

The Athenian Stranger joins the other two on their religious pilgrimage from Knossos, on Crete to the cave of Zeus on Mount Ida. The entire dialogue takes place during this journey, which mimics the action of Minos: said by the Cretans to have made their ancient laws, Minos walked this path every nine years in order to receive instruction from Zeus on lawgiving. It is also said to be the longest day of the year, allowing for the densely packed twelve books. The question asked at the beginning is not "What is law?" as one would expect. That is the question of the Platonic dialogue Minos. The dialogue rather proceeds from the question, "who it is that receives credit for creating laws." By the end of the third book Cleinias announces that he has in fact been given the responsibility of creating the laws for a new Cretan colony, and that he would like the Athenian stranger's assistance. The rest of the dialogue proceeds with the three old men, walking towards the cave and making laws for this new city which is called the city of Magnesia.

While traveling from Knossos to the shrine of Zeus on Mount Ida, the Athenian begins by asking if the other two attribute their laws to a divine or a human origin. Both Clinias and Megillus say that their laws have a divine origin. The laws of Crete are said to come from Minos and Rhadamanthus, who consulted with Zeus.

The questions of the Laws are quite numerous, including:

The dialogue uses primarily the Athenian and Spartan (Lacedaemonian) law systems as background for pinpointing a choice of laws, which the speakers imagine as a more or less coherent set for the new city they are talking about.

The tenth book of the Laws most famously discusses the priority of soul: both explanatory priority and ontological priority. Plato here refutes the views of his predecessors who argued that soul (and what soul is related to, such as intelligence, knowledge, skill, etc.) is posterior to corporeal things such as earth and fire. The natural philosophers had explained soul, intelligence, and so on, in terms of corporeal things: corporeal things exist first and give rise to psychic phenomena. In contrast, Plato argues that soul is first, both as that in terms of which corporeal things ought to be explained and as that which gives rise to the corporeal world. Plato concludes this by relying on his view that the soul is intelligent and a self-mover and that soul is that which supervises the cosmos. There is an important scholarly discussion of whether Plato means to allow for there to be an evil soul governing the cosmos, alongside a virtuous soul. Gabriela Carone, for instance, maintains that Plato "does not dismiss the existence of a kind of evil soul as such." But more-recent scholarship has argued otherwise. In general, recent scholars have understood Plato's psychology to be such that souls are by their very nature intelligent (for it is by means of their intelligence that they move things), and that Plato's view of intelligence requires that intelligent things not be vicious; this rules out the very possibility of an evil soul.

The Laws, like the earlier Republic, concerns the making of a city in speech. Yet it is in opposition to the earlier dialogue, and the constitution of the hypothetical Magnesia described in the Laws differs from that of Kallipolis described in the Republic, on several key points. The city of the Laws differs in its allowance of private property and private families, and in the very existence of written laws, from the city of the Republic, with its property-system and community of wives for the guardians, and absence of written law.