The Roman magistrate, soldier, and engineer Sextus Julius Frontinus (ca. 35-ca. 104) is known primarily as a technical writer.

Frontinus seems to have been of patrician descent, and his writings indicate that he had some knowledge of Alexandrian mathematics. In his role as magistrate, Frontinus served as praetor urbanus of Rome in the year 70 and as consul suffectus in 73. From 74 to 78 he served as governor of Britain, during which time he subdued the Silures, a powerful and warlike tribe from Wales. His instinct for public improvements, which dominated his whole career, led him to begin the construction of a public highway (Via Julia) in the conquered territory. Returning to Rome in 78, Frontinus served as consul suffectus in 98 and again in 100. It was during this latter period that most of his writings seem to have been composed.

Appointed curator aquarum (superintendent of the aqueducts) of Rome in 97, Frontinus embodied his knowledge of the water supply in a treatise, On the Aqueducts of Rome, a valuable source of information on the historical, legal, and technical life of the times. In this work Frontinus lists the names of the aqueducts, when and by whom they were constructed, and their size, height, and distribution, and he collects the many laws and penalties regulating their proper employment. The treatise portrays Frontinus as a faithful public servant who openly boasts that his reforms have made the city cleaner and the water and the air purer and removed the causes of pestilence which had formerly given Rome a bad reputation. In this work Frontinus shows himself aware of the relationship between the speed of outflow of water and its height.

Frontinus composed two treatises on military tactics. The first, The Stratagems, is a manual on military stratagems compiled from Greek and Roman military history. The book is divided into three parts--stratagems for use before the battle begins, those concerned with the battle itself, and those concerned with sieges and the raising of sieges. The other military treatise, De re militari, has not survived except in fragments quoted by other authorities.

Frontinus also composed a treatise on the art of surveying, of which only fragments are extant. It appears that this work was a pioneering effort in Roman surveying and that it was used as a standard authority for some years.