The executive magistrates of the Roman Republic were officials of the ancient Roman Republic (c. 510 BC – 44 BC), elected by the People of Rome. Ordinary magistrates (magistratus) were divided into several ranks according to their role and the power they wielded: censors, consuls (who functioned as the regular head of state), praetors, curule aediles, and finally quaestor. Any magistrate could obstruct (veto) an action that was being taken by a magistrate with an equal or lower degree of magisterial powers. By definition, plebeian tribunes and plebeian aediles were technically not magistrates as they were elected only by the plebeians, but no ordinary magistrate could veto any of their actions. Dictator was an extraordinary magistrate normally elected in times of emergency (usually military) for a short period. During this period, the dictator's power over the Roman government was absolute, as they were not checked by any institution or magistrate.

The magistrates (magistratus) were elected by the People of Rome, which consisted of plebeians (commoners) and patricians (aristocrats). Each magistrate was vested with a degree of power, called "major powers" or maior potestas. Dictators had more "major powers" than any other magistrate, and thus they outranked all other magistrates; but were originally intended only to be a temporary tool for times of state emergency. Thereafter in descending order came the censor (who, while the highest-ranking ordinary magistrate by virtue of his prestige, held little real power), the consul, the praetor, the curule aedile, and the quaestor. Any magistrate could obstruct (veto) an action that was being taken by a magistrate with an equal or lower degree of magisterial powers. If this obstruction occurred between two magistrates of equal rank, such as two praetors, then it was called par potestas (negation of powers). To prevent this, magistrates used a principle of alteration, assigned responsibilities by lot or seniority, or gave certain magistrates control over certain functions. If this obstruction occurred against a magistrate of a lower rank, then it was called intercessio, where the magistrate literally interposed his higher rank to obstruct the lower-ranking magistrate. By definition, plebeian tribunes and plebeian aediles were technically not magistrates since they were elected only by the plebeians. As such, no ordinary magistrate could veto any of their actions.

Only Roman citizens (both plebeians and patricians) had the right to confer magisterial powers (potestas) on any individual magistrate. The most important power was imperium, which was held by consuls (the chief magistrates) and by praetors (the second highest-ranking ordinary magistrate). Defined narrowly, imperium simply gave a magistrate the authority to command a military force. Defined more broadly, however, imperium gave a magistrate the constitutional authority to issue commands (military, diplomatic, civil, or otherwise). A magistrate's imperium was at its apex while the magistrate was abroad. While the magistrate was in the city of Rome itself, however, he had to completely surrender his imperium, so that liberty (libertas) was maximized. Magistrates with imperium sat in a curule chair, and were attended by lictors (bodyguards) who carried axes called fasces which symbolized the power of the state to punish and to execute. Only a magistrate with imperium could wear a bordered toga, or be awarded a triumph.

All magistrates had the power of coercion (coercitio), which was used by magistrates to maintain public order. A magistrate had many ways with which to enforce this power. Examples include flogging, imprisonment, fines, mandating pledges and oaths, enslavement, banishment, and sometimes even the destruction of a person's house. While in Rome, all citizens had an absolute protection against Coercion. This protection was called "Provocatio" (see below), which allowed any citizen to appeal any punishment. However, the power of Coercion outside the city of Rome was absolute. Magistrates also had both the power and the duty to look for omens from the Gods (auspicia), which could be used to obstruct political opponents. By claiming to witness an omen, a magistrate could justify the decision to end a legislative or senate meeting, or the decision to veto a colleague. While the magistrates had access to oracular documents, the Sibylline books, they rarely consulted with these books, and even then, only after seeing an omen. All senior magistrates (consuls, praetors, censors, and plebeian tribunes) were required to actively look for omens (auspicia impetrativa); simply having omens thrust upon them (auspicia oblativa) was generally not adequate. Omens could be discovered while observing the heavens, while studying the flight of birds, or while studying the entrails of sacrificed animals. When a magistrate believed that he had witnessed such an omen, he usually had a priest (augur) interpret the omen. A magistrate was required to look for omens while presiding over a legislative or senate meeting, and while preparing for a war.

One check over a magistrate's power was collegiality (collega), which required that each magisterial office be held concurrently by at least two people. For example, two consuls always served together. The check on the magistrate's power of Coercion was Provocatio, which was an early form of due process (habeas corpus). Any Roman citizen had the absolute right to appeal any ruling by a magistrate to a plebeian tribune. In this case, the citizen would cry "provoco ad populum", which required the magistrate to wait for a tribune to intervene, and make a ruling. Sometimes, the case was brought before the College of tribunes, and sometimes before the Plebeian Council (popular assembly). Since no tribune could retain his powers outside of the city of Rome, the power of Coercion here was absolute. An additional check over a magistrate's power was that of Provincia, which required a division of responsibilities.

Once a magistrate's annual term in office expired, he had to wait ten years before serving in that office again. Since this did create problems for some magistrates (in particular, consuls and praetors), these magistrates occasionally had their imperium "prorogued" (prorogare), which allowed them to retain the powers of the office as a Promagistrate. The result was that private citizens ended up with consular and praetorian imperium, without actually holding either office. Often, they used this power to act as provincial governors.

The consul of the Roman Republic was the highest-ranking ordinary magistrate. Two consuls were elected for an annual term (from January through December) by the assembly of Roman citizens, the Centuriate Assembly. After they were elected, they were granted imperium powers by the assembly. If a consul died before his term ended, another consul (the consul suffectus), was elected to complete the original consular term. Throughout the year, one consul was superior in rank to the other consul. This ranking flipped every month, between the two consuls. Once a consul's term ended, he held the honorary title of consulare for the rest of his time in the senate, and had to wait for ten years before standing for re-election to the consulship. Consuls had supreme power in both civil and military matters, which was due, in part, to the fact that they held the highest ordinary grade of imperium (command) powers. While in the city of Rome, the consul was the head of the Roman government. While components of public administration were delegated to other magistrates, the management of the government was under the ultimate authority of the consul. The consuls presided over the Roman Senate and the Roman assemblies, and had the ultimate responsibility to enforce policies and laws enacted by both institutions. The consul was the chief diplomat, carried out business with foreign nations, and facilitated interactions between foreign ambassadors and the senate. Upon an order by the senate, the consul was responsible for raising and commanding an army. While the consuls had supreme military authority, they had to be provided with financial resources by the Roman Senate while they were commanding their armies. While abroad, the consul had absolute power over his soldiers, and over any Roman province.

The praetors administered civil law and commanded provincial armies, and, eventually, began to act as chief judges over the courts. Praetors usually stood for election with the consuls before the assembly of the soldiers, the Centuriate Assembly. After they were elected, they were granted imperium powers by the assembly. In the absence of both senior and junior consuls from the city, the Urban praetor governed Rome, and presided over the Roman Senate and Roman assemblies. Other praetors had foreign affairs-related responsibilities, and often acted as governors of the provinces. Since praetors held imperium powers, they could command an army.