Forum, in ancient Roman cities, an open place used for the administration of justice or the sale of goods, and for the transaction of all kinds of public business. In this respect it corresponded with the agora of the Greeks; but unlike this, it was oblong in form, and never square. In a Roman camp it was the open space before the tent of the general, and the word also forms a part of the name of many towns and villages. The Romans had two kinds of fora, the civilia, sometimes called judicialia, in which popular assemblies and courts of justice were held, and where the bankers and usurers usually had their stands; and the venalia, which were used exclusively for mercantile purposes. The city of Rome contained 19 of both kinds; but the forum Ro-manum, whose origin is coeval with that of the city, and which is known by the general name of the Forum, was by far the most important, notwithstanding some very magnificent ones were built under the emperors. It occupied a hollow space between the Capito-line and Palatine hills, extending in its longest diameter probably from the arch of Septimius Severus to the temple of Antoninus and Faustina. Around its four sides stood temples, basilicas, triumphal arches, and other public edifices, while within it were the rostra or stages from which orators addressed public assemblies, statues of illustrious Romans, columns, and trophies of war.

At the comitium or upper end were suspended the laws of the twelve tables, and the fasti or calendar of all the days on which legal business could be transacted before the praetor. It is now known as the Campo Vaccino, from having been used for several centuries as a cattle market, and preserves no traces of its ancient splendor beyond a few scattered columns. A forum judiciale was built by Julius Caesar, and another by Augustus, which, with the forum Romanum, seem to have been the only ones in Rome for the transaction of public business.