The praetor was a high magistrate in ancient Rome (republic and principate) vested with judicial functions in civil trials (jurisdictio) and commanding power (imperium) in the broadest meaning of the term.
In the official hierarchy he ranked after the consuls. Praetorship was introduced in 367 B.C. as a praetorian magistracy; but already in 337 B.C. plebeians were admitted thereto. From 242 B.C. distinction was made between the urban praetor (p. urbanus), vested with jurisdiction in controversies between Roman citizens, and the p. peregrines for civil trials in which aliens (peregrini) were involved.
Important factors in the development of the law were the praetorian edicts in which the praetors introduced new actions and procedural measures for the protection of legal situations to which the earlier jus civile did not grant such protection. The Roman law was reformed considerably by this praetorian law (jus praetorium) in many directions (such as succession, obligations, procedure) and lost much of its archaic formalism. The number of praetors increased eventually to 16, their duties having been extended to include control of provincial administration.