Gaius Furius Sabinius Aquila Timesitheus (Greek: Τιμησίθεος) (AD 190-243) was an officer of the Roman Imperial government in the first half of the 3rd century. Most likely of Oriental-Greek origins, he was a Roman citizen, probably of equestrian rank.

He began his career in the Imperial Service as the commander of a cohort of auxiliary infantry and rose to become Praetorian Prefect, the highest office in the Imperial hierarchy, with both civilian and military functions. His official life was spent mainly in fiscal postings and he typified the powerful procuratorial functionaries who came to dominate the Imperial government in the second quarter of the Third Century. Although he was on several occasions appointed to positions that contemporary Administrative Law reserved for officials of senatorial rank, he remained an equestrian until his death; it is possible that he deliberately avoided adlection to the Roman Senate, preferring to exercise power in offices from which senators were excluded.

He either died of illness or was murdered in the course of a successful campaign against the Sasanians under king Shapur I in Mesopotamia.

"Timesitheus" is a cognomen which suggests that the bearer was ethnically a Greek. However, Timesitheus's praenomen and nomen (i.e. "Gaius" and "Furius Sabinius" respectively) indicate long-established Roman citizenship and a family that was well-integrated into the élite classes of the Empire although it is otherwise unknown. Such enthusiasm to be associated with the Imperial power was not unknown in the case of ambitious Greek families. His origins could have been anywhere in the eastern provinces where Greek, rather than Latin, was the dominant culture. Somewhere in Asia Minor is a possibility. However, as will be seen, his early career supports the notion that he may have had some connection to the Severan Dynasty, in particular the "Syrian Princesses". This could indicate that his origins were in the Oriens - i.e. the modern Levant /Arabia.

Despite the obscurity of his family background, his reputation and his achievements suggest that he benefitted from an excellent classical education. His parents were almost certainly wealthy and, most likely, of equestrian status.

Timesitheus' career before his appointment as Praetorian Prefect is recorded on an inscription on a statue from Lugdunum in the province of Gallia Lugdunensis (Lyon, France).

Late in the reign of Septimius Severus, or during the reign of Caracalla, Timesitheus was Prefect of Cohors I Gallicae in the province of Hispania Tarraconensis (Mediterranean Spain). This appointment was a typical first step for an equestrian seeking a career in the imperial service under the so-called Tres militiae system. Under that system Timesitheus might have been expected to go on to two additional junior military prefectures, firstly of a legionary cohort and then of an ala (Roman cavalry unit). Only then would most aspiring equestrian functionaries have been considered eligible for appointment as a procurator (financial administrator), the usual first step to high office in the Equestrian Service. However, Timesitheus seems to have missed out these two stages in the equestrian cursus and is next recorded as the Procurator Rationis Privatae (superintendent of the private properties of the Imperial Family) in the provinces of Belgica (north-east Gaul),Germania Inferior (the northern section of the Roman-controlled Rhineland) and Germania Superior (the southern section of the Roman Rhineland). He probably held this office under Caracalla. This position carried the equestrian rank of sexagenarius, indicating that he had thus became a member of that class of equestrian functionaries who were paid a nominal salary of 60,000ss/annum.

His next recorded appointment was as Procurator provinciae Arabiae (financial administrator of the province of Arabia Petraea). With this posting Timesitheus became a centenarius (nominal salary 100,000ss/annum). In addition to his procuratorship he also served on two occasions (218 and 222 AD)) as vice praeses of the province - i.e., he acted as its governor (in place of a senatorial legatus). In this capacity he would have commanded Legio III Cyrenaica. Timesitheus was en poste as acting-governor in 222 AD and may have played a part in the overthrow of the equestrian usurper Marcus Opellius Macrinus in favour of Elagabalus. This service to the Severan dynasty might explain his continued rise under the regime of the "Syrian Princesses" who would certainly have been responsible for his appointment as Procurator in urbe Magister XX heredatium (collector of the one-twentieth - 5% - tax on inheritances in Rome), a post conferring ducenarius rank (salary 200.000ss/annum), and, at the same time, Logista Thymelae (Superintendent of the Imperial Theatre Properties). The office of Magister XX heredatium was an important financial post requiring expert administration. However, as holder of that office and that of logista Timesitheus also became a member of the court-circle. That may well have been the main object of the Syrian Princesses in securing him these appointments - to move a man who had proved his loyalty to them into a position where he would be able to exert influence on their behalf in areas well beyond the limits of the job-descriptions pertaining to his specific offices. As far as Timesitheus's career was concerned, his access to Imperial patronage as a palatinus, or courtier, would have effectively set him above less-favoured ducenarii officials in the competition for procuratorial postings; there followed two important appointments which were associated with the two major wars fought by Alexander Severus, first against the renascent Persian Empire (232 AD) and then against the league of German Peoples who were to become known to the Romans as the Alemanni (234-5 AD) in which Timesitheus's assorted military and procuratorial competencies would, perhaps, have been particularly useful to the regime.