The Roman triumph (triumphus) was a civil ceremony and religious rite of ancient Rome, held to publicly celebrate and sanctify the success of a military commander who had led Roman forces to victory in the service of the state or, in some historical traditions, one who had successfully completed a foreign war.

On the day of his triumph, the general wore a crown of laurel and an all-purple, gold-embroidered triumphal toga picta ("painted" toga), regalia that identified him as near-divine or near-kingly. In some accounts, his face was painted red, perhaps in imitation of Rome's highest and most powerful god, Jupiter. The general rode in a four-horse chariot through the streets of Rome in unarmed procession with his army, captives, and the spoils of his war. At Jupiter's temple on the Capitoline Hill, he offered sacrifice and the tokens of his victory to Jupiter.

In Republican tradition, only the Senate could grant a triumph. The origins and development of this honour are obscure: Roman historians themselves placed the first triumph in the mythic past. Republican morality required that the general conduct himself with dignified humility, as a mortal citizen who triumphed on behalf of Rome's Senate, people, and gods. Inevitably, the triumph offered the general extraordinary opportunities for self-publicity, besides its religious and military dimensions. Most triumphal celebrations included a range of popular games and entertainments for the Roman masses.

Most Roman festivals were calendar fixtures, tied to the worship of particular deities. While the triumphal procession culminated at Jupiter's temple on the far end of the Via Sacra (sacred road) in the Roman Forum, the procession itself, attendant feasting, and public games promoted the general's status and achievement. By the Late Republican era, triumphs were drawn out and extravagant, motivated by increasing competition among the military-political adventurers who ran Rome's nascent empire. Some triumphs were prolonged by several days of public games and entertainments. From the Principate onwards, the triumph reflected the Imperial order and the pre-eminence of the Imperial family. The triumph was consciously imitated by medieval and later states in the royal entry and other ceremonial events.

In Republican Rome, truly exceptional military achievement merited the highest possible honours, which connected the vir triumphalis ("man of triumph", later known as a triumphator) to Rome's mythical and semi-mythical past. In effect, the general was close to being "king for a day", and possibly close to divinity. He wore the regalia traditionally associated both with the ancient Roman monarchy and with the statue of Jupiter Capitolinus: the purple and gold "toga picta", laurel crown, red boots and, again possibly, the red-painted face of Rome's supreme deity. He was drawn in procession through the city in a four-horse chariot, under the gaze of his peers and an applauding crowd, to the temple of Capitoline Jupiter. His spoils and captives led the way; his armies followed behind. Once at the Capitoline temple, he sacrificed two white oxen to Jupiter, and laid tokens of victory at the feet of Jupiter's statue, thus dedicating the triumph to the Roman Senate, people, and gods.

Triumphs were tied to no particular day, season, or religious festival of the Roman calendar. Most seem to have been celebrated at the earliest practicable opportunity, probably on days that were deemed auspicious for the occasion. Tradition required that, for the duration of a triumph, every temple was open. The ceremony was thus, in some sense, shared by the whole community of Roman gods, but overlaps were inevitable with specific festivals and anniversaries. Some may have been coincidental; others were designed. For example, March 1, the festival and dies natalis of the war god Mars, was the traditional anniversary of the first triumph by Publicola (504 BCE), of six other Republican triumphs, and of the very first Roman triumph by Romulus. Pompey postponed his third and most magnificent triumph for several months to make it coincide with his own dies natalis (birthday).

Religious dimensions aside, the focus of the triumph was the general himself. The ceremony promoted him – however temporarily – above every mortal Roman. This was an opportunity granted to very few. From the time of Scipio Africanus, the triumphal general was linked (at least for historians during the Principate) to Alexander and the demi-god Hercules, who had laboured selflessly for the benefit of all mankind. His sumptuous triumphal chariot was bedecked with charms against the possible envy (invidia) and malice of onlookers. In some accounts, a companion or public slave would remind him from time to time of his own mortality (a memento mori).

Rome's earliest "triumphs" were probably simple victory parades, celebrating the return of a victorious general and his army to the city, along with the fruits of his victory, and ending with some form of dedication to the gods. This is probably so for the earliest legendary and later semi-legendary triumphs of Rome's regal era, when the king functioned as Rome's highest magistrate and war-leader. As Rome's population, power, influence, and territory increased, so did the scale, length, variety, and extravagance of its triumphal processions.