Ancient Roman temples were among the most important buildings in Roman culture, and some of the richest buildings in Roman architecture, though only a few survive in any sort of complete state. Today they remain "the most obvious symbol of Roman architecture". Their construction and maintenance was a major part of ancient Roman religion, and all towns of any importance had at least one main temple, as well as smaller shrines. The main room (cella) housed the cult image of the deity to whom the temple was dedicated, and often a table for supplementary offerings or libations and a small altar for incense. Behind the cella was a room, or rooms, used by temple attendants for storage of equipment and offerings. The ordinary worshiper rarely entered the cella, and most public ceremonies were performed outside of the cella where the sacrificial altar was located, on the portico, with a crowd gathered in the temple precinct.

The most common architectural plan had a rectangular temple raised on a high podium, with a clear front with a portico at the top of steps, and a triangular pediment above columns. The sides and rear of the building had much less architectural emphasis, and typically no entrances. There were also circular plans, generally with columns all round, and outside Italy there were many compromises with traditional local styles. The Roman form of temple developed initially from Etruscan temples, themselves influenced by the Greeks, with subsequent heavy direct influence from Greece.

Public religious ceremonies of the official Roman religion took place outdoors and not within the temple building. Some ceremonies were processions that started at, visited, or ended with a temple or shrine, where a ritual object might be stored and brought out for use, or where an offering would be deposited. Sacrifices, chiefly of animals, would take place at an open-air altar within the templum; often on one of the narrow extensions of the podium to the side of the steps. Especially under the Empire, exotic foreign cults gained followers in Rome, and were the local religions in large parts of the expanded Empire. These often had very different practices, some preferring underground places of worship, while others, like Early Christians, worshiped in houses.

Some remains of many Roman temples still survive, above all in Rome itself, but the relatively few near-complete examples were nearly all converted into Christian churches (and sometimes subsequently to mosques), usually a considerable time after the initial triumph of Christianity under Constantine. The decline of Roman religion was relatively slow, and the temples themselves were not appropriated by the government until a decree of the Emperor Honorius in 415. Santi Cosma e Damiano, in the Roman Forum, originally the Temple of Romulus, was not dedicated as a church until 527. The best known is the Pantheon, Rome, which, however, is highly untypical, being a very large circular temple with a magnificent concrete roof, behind a conventional portico front.

The English word "temple" derives from the Latin templum, which was originally not the building itself, but a sacred space surveyed and plotted ritually. The Roman architect Vitruvius always uses the word templum to refer to the sacred precinct, and not to the building. The more common Latin words for a temple or shrine were sacellum (a small shrine or chapel), aedes, delubrum, and fanum (in this article, the English word "temple" refers to any of these buildings, and the Latin templum to the sacred precinct).

The form of the Roman temple was mainly derived from the Etruscan model, but in the late Republic there was a switch to using Greek classical and Hellenistic styles, without much change in the key features of the form. The Etruscans were a people of northern Italy, whose civilization was at its peak in the seventh century BC. The Etruscans were already influenced by early Greek architecture, so Roman temples were distinctive but with both Etruscan and Greek features. Surviving temples (both Greek and Roman) lack the extensive painted statuary that decorated the rooflines, and the elaborate revetments and antefixes, in colourful terracotta in earlier examples, that enlivened the entablature.

Etruscan and Roman temples emphasised the front of the building, which followed Greek temple models and typically consisted of wide steps leading to a portico with columns, a pronaos, and usually a triangular pediment above, which was filled with statuary in the most grand examples; this was as often in terracotta as stone, and no examples have survived except as fragments. Especially in the earlier periods, further statuary might be placed on the roof, and the entablature decorated with antefixes and other elements, all of this being brightly painted. However, unlike the Greek models, which generally gave equal treatment to all sides of the temple, which could be viewed and approached from all directions, the side and rear walls of Roman temples might be largely undecorated (as in the Pantheon, Rome and Vic), inaccessible by steps (as in the Maison Carrée and Vic), and even back on to other buildings. As in the Maison Carrée, columns at the side might be half columns, emerging from ("engaged with" in architectural terminology) the wall.

The platform on which the temple sat was typically raised higher in Etruscan and Roman examples than Greek, with up to ten, twelve or more steps rather than the three typical in Greek temples; the Temple of Claudius was raised twenty steps. These steps were normally only at the front, and typically not the whole width of that. It might or might not be possible to walk around the temple exterior inside (Temple of Hadrian) or outside the colonnade, or at least down the sides. The description of the Greek models used here is a generalization of classical Greek ideals, and later Hellenistic buildings often do not reflect them. For example, the "Temple of Dionysus" on the terrace by the theatre at Pergamon (Ionic, 2nd century BC, on a hillside), had many steps in front, and no columns beyond the portico. The Parthenon, also approached up a hill, probably had many wide steps at the approach to the main front, followed by a flat area before the final few steps.