Hadrian was born in Italica, close to modern Seville in Spain, an Italic settlement in Hispania Baetica; his branch of the Aelia gens, the Aeli Hadriani, came from the town of Hadria in eastern Italy.

Although they were considered to be, in the words of Aurelius Victor, advenae ("aliens", people "from the outside"), both Trajan and Hadrian were of Italic lineage and belonged to the upper class of Roman society.

[41][42] Late in Trajan's reign, Hadrian failed to achieve a senior consulship, being only suffect consul for 108;[43] this gave him parity of status with other members of the senatorial nobility,[44] but no particular distinction befitting an heir designate.

In Rome, Hadrian's former guardian and current praetorian prefect, Attianus, claimed to have uncovered a conspiracy involving Lusius Quietus and three other leading senators, Lucius Publilius Celsus, Aulus Cornelius Palma Frontonianus and Gaius Avidius Nigrinus.

[67] The Historia Augusta describes Palma and a third executed senator, Lucius Publilius Celsus (consul for the second time in 113), as Hadrian's personal enemies, who had spoken in public against him.

[76] Some sources describe Hadrian's occasional recourse to a network of informers, the frumentarii,[77] to discreetly investigate persons of high social standing, including senators and his close friends.

[100] When Hadrian arrived on the Euphrates, he personally negotiated a settlement with the Parthian King Osroes I, inspected the Roman defences, then set off westwards, along the Black Sea coast.

[111] Generally Hadrian preferred that Greek notables, including priests of the imperial cult, focus on more essential and durable provisions, especially munera such as aqueducts and public fountains (nymphaea).

[112] Athens was given two nymphaea; one brought water from Mount Parnes to the Athenia Agora via a complex, challenging and ambitious system of aqueduct tunnels and reservoirs, to be constructed over several years.

As Pompey was universally acknowledged as responsible for establishing Rome's power in the east, this restoration was probably linked to a need to reaffirm Roman Eastern hegemony following social unrest there during Trajan's late reign.

[135] Successful applications for membership involved mythologised or fabricated claims to Greek origins, and affirmations of loyalty to imperial Rome, to satisfy Hadrian's personal, idealised notions of Hellenism.

[138] Epigraphical evidence suggests that the prospect of applying to the Panhellenion held little attraction to the wealthier, Hellenised cities of Asia Minor, which were jealous of Athenian and European Greek preeminence within Hadrian's scheme.

[153] The scholar Peter Schäfer maintains that there is no evidence for this claim, given the notoriously problematical nature of the Historia Augusta as a source, the "tomfoolery" shown by the writer in the relevant passage, and the fact that contemporary Roman legislation on "genital mutilation" seems to address the general issue of castration of slaves by their masters.

[184] Dio Cassius and the Historia Augusta record details of his failing health; some modern sources interpret the ear-creases on later portrayals (such as the Townley Hadrian) as signs of coronary artery disease.

He focused on protection from external and internal threats; on "raising" existing provinces rather than the aggressive acquisition of wealth and territory through subjugation of "foreign" peoples that had characterised the early empire.

Between 131 and 132, he sent Hadrian a lengthy letter (Periplus of the Euxine) on a maritime trip around the Black Sea that was intended to offer relevant information in case a Roman intervention was needed.

[205] Faced with a shortage of legionary recruits from Italy and other Romanised provinces, Hadrian systematised the use of less costly numeri – ethnic non-citizen troops with special weapons, such as Eastern mounted archers, in low-intensity, mobile defensive tasks such as dealing with border infiltrators and skirmishers.

[216] Hadrian codified the customary legal privileges of the wealthiest, most influential, highest-status citizens (described as splendidiores personae or honestiores), who held a traditional right to pay fines when found guilty of relatively minor, non-treasonous offences.

Hadrian found it necessary to clarify that decurions, the usually middle-class, elected local officials responsible for running the ordinary, everyday official business of the provinces, counted as honestiores; so did soldiers, veterans and their families, as far as civil law was concerned; by implication, almost all citizens below those ranks – the vast majority of the Empire's population – counted as humiliores, with low citizen status, high tax obligations and limited rights.

[246] In a rescript addressed to the proconsul of Asia, Gaius Minicius Fundanus, and preserved by Justin Martyr, Hadrian laid down that accusers of Christians had to bear the burden of proof for their denunciations[247] or be punished for calumnia (defamation).

Examples in the Roman Province of Thrace include monumental developments to the Stadium and Odeon of Philippopolis (present-day Plovdiv), the provincial capital,[249] and his rebuilding and enlargement of the city of Orestias, which he renamed Hadrianopolis (modern Edirne).

Hadrian's Villa at Tibur (Tivoli) provides the greatest Roman equivalent of an Alexandrian garden, complete with domed Serapeum, recreating a sacred landscape.

Dio claims that once Hadrian became emperor, he showed Apollodorus drawings of the gigantic Temple of Venus and Roma, implying that great buildings could be created without his help.

[274] Hadrian has been described as the most versatile of all Roman emperors, who "adroitly concealed a mind envious, melancholy, hedonistic, and excessive with respect to his own ostentation; he simulated restraint, affability, clemency, and conversely disguised the ardor for fame with which he burned.

[285] While the balance of ancient literary opinion almost invariably compares Hadrian unfavourably to his predecessor, modern historians have sought to examine his motives, purposes and the consequences of his actions and policies.

Levi, a summing-up of Hadrian's policies should stress the ecumenical character of the Empire, his development of an alternate bureaucracy disconnected from the Senate and adapted to the needs of an "enlightened" autocracy, and his overall defensive strategy; this would qualify him as a grand Roman political reformer, creator of an openly absolute monarchy to replace a sham senatorial republic.

A juvenile type with curly hair, broad side burns and a light moustache (but a free chin) was shown on coins later in his life on rare aurei, but likely reflects an early portrait before he became emperor.

The collection as a whole is notorious for its unreliability ("a mish mash of actual fact, cloak and dagger, sword and sandal, with a sprinkling of Ubu Roi"),[297] but most modern historians consider its account of Hadrian to be relatively free of outright fictions, and probably based on sound historical sources,[298] principally one of a lost series of imperial biographies by the prominent 3rd-century senator Marius Maximus, who covered the reigns of Nerva through to Elagabalus.

[299] The first modern historian to produce a chronological account of Hadrian's life, supplementing the written sources with other epigraphical, numismatic, and archaeological evidence, was the German 19th-century medievalist Ferdinand Gregorovius.

[300] A 1907 biography by Weber,[300] a German nationalist and later Nazi Party supporter, incorporates the same archaeological evidence to produce an account of Hadrian, and especially his Bar Kokhba war, that has been described as ideologically loaded.