The Lares were the protective spirits of the Roman household — the guardian-divinities of the dwelling itself, of the family's boundaries, and (in a separate but related cult) of the crossroads and the property-lines outside. They were honored in every Roman home at the lararium — a small shrine, often built into the wall of the atrium, decorated with paintings of two dancing youths in short tunics raising drinking-horns above their heads, with a serpent (the protective genius of the place) often depicted below. Daily offerings were made: a small portion of every meal was set aside for them, and on special days (the Kalends, Nones, and Ides of every month, family birthdays, marriages, and journeys) more elaborate sacrifices were offered. They were invoked at every important domestic moment — the bringing-home of a bride, the birth of a child, the assumption of the toga virilis by a son, the family's departure on a journey or return.

There were several distinct types of Lares. The Lares Familiares (or Lares Domestici) were the household-spirits proper, presiding over the dwelling and the family. The Lares Compitales were the crossroads-spirits, honored at the small shrines (compita) that stood at the meeting of property lines and rural lanes; their festival, the Compitalia, was held annually shortly after the winter solstice and was an occasion for slaves and free to celebrate together (since the crossroads were liminal places where social distinctions were temporarily suspended). The Lares Praestites were the public Lares of the city of Rome itself, whose temple stood at the head of the Sacred Way. The Lares Permarini were the protectors of seafarers. The Lares Viales protected travelers on the roads. The category was elastic and could be multiplied as occasion required.

The origin of the Lares was much disputed in antiquity. The most plausible interpretation, supported by both ancient testimony (Varro and others) and modern scholarship, is that they were originally the spirits of the dead — particularly of the family's ancestors, whose protective power continued to bear upon the dwelling they had once inhabited — and that their cult and that of the Manes (treated below) were anciently overlapping. By the historical period the two had largely separated, with the Lares as the protective spirits of the place and the Manes as the dead generally; but the original connection is still detectable in the iconography and in the patterns of cult.