Tiberius was born in
Rome on 16 November 42 BC to
Tiberius Claudius Nero and
 In 39 BC his mother
divorced his biological father and remarried
Gaius Julius Caesar Octavianus shortly thereafter, while still pregnant with Tiberius Nero's son. In 38 BC his brother,
Nero Claudius Drusus, was born.
Little is recorded of Tiberius's early life. In 32 BC Tiberius at the age of nine, delivered the
eulogy for his biological father at the
 In 29 BC, he rode in the triumphal chariot along with his adoptive father Octavian in celebration of the
defeat of Antony and Cleopatra at Actium.
In 23 BC Emperor Augustus became gravely ill and his possible death threatened to plunge the Roman world into chaos again. Historians generally agree that it is during this time that the question of Augustus' heir became most acute, and while Augustus had seemed to indicate that
Marcellus would carry on his position in the event of his death, the ambiguity of succession became Augustus' chief problem.
In response, a series of potential heirs seem to have been selected, among them Tiberius and his brother Drusus. In 24 BC at the age of seventeen Tiberius entered politics under Augustus' direction, receiving the position of
 and was granted the right to stand for election as
consul five years in advance of the age required by law.
 Similar provisions were made for Drusus.
Civil and military career
Shortly thereafter Tiberius began appearing in court as an
 and it is presumably here that his interest in Greek
rhetoric began. In 20 BC, Tiberius was sent East under
Marcus Vipsanius Agrippa.
Parthian Empire had captured the standards of the
legions under the command of
Marcus Licinius Crassus (53 BC) (at the
Battle of Carrhae), Decidius Saxa (40 BC), and
Mark Antony (36 BC).
After a year of negotiation, Tiberius led a sizable force into
Armenia, presumably with the goal of establishing it as a Roman
client state and ending the threat it posed on the Roman-Parthian border. Augustus was able to reach a compromise whereby the standards were returned, and Armenia remained a neutral territory between the two powers.
Vipsania Agrippina, the daughter of Augustus’s close friend and greatest general,
Marcus Vipsanius Agrippa.
 He was appointed to the position of
praetor, and sent with his legions to assist his brother Drusus in campaigns in the west. While Drusus focused his forces in
Gallia Narbonensis and along the German frontier, Tiberius combated the tribes in the
Alps and within
conquering Raetia. In 15 BC he discovered the sources of the
Danube, and soon afterwards the bend of the middle course.
 Returning to Rome in 13 BC, Tiberius was appointed as consul, and around this same time his son,
Drusus Julius Caesar, was born.
Agrippa's death in 12 BC elevated Tiberius and Drusus with respect to the succession. At Augustus’ request in 11 BC, Tiberius divorced Vipsania and married
Julia the Elder, Augustus' daughter and Agrippa's widow.
 Tiberius was very reluctant to do this, as Julia had made advances to him when she was married and Tiberius was happily married. His new marriage with Julia was happy at first, but turned sour.
Reportedly, Tiberius once ran into Vipsania again, and proceeded to follow her home crying and begging forgiveness;
 soon afterwards, Tiberius met with Augustus, and steps were taken to ensure that Tiberius and Vipsania would never meet again.
 Tiberius continued to be elevated by Augustus, and after Agrippa's death and his brother Drusus' death in 9 BC, seemed the clear candidate for succession. As such, in 12 BC he received military commissions in
Germania; both areas highly volatile and of key importance to Augustan policy.
In 6 BC, Tiberius launched a
pincer movement against the
Marcomanni. Setting out northwest from
Carnuntum on the Danube with four legions, Tiberius passed through
Quadi territory in order to invade the Marcomanni from the east. Meanwhile, general
Gaius Sentius Saturninus would depart east from
Moguntiacum on the Rhine with two or three legions, pass through newly annexed
Hermunduri territory, and attack the Marcomanni from the west. The campaign was a resounding success, but Tiberius could not subjugate the Marcomanni because he was soon summoned to the Rhine frontier to protect Rome's new conquests in Germania.
He returned to Rome and was consul for a second time in 7 BC, and in 6 BC was granted
tribunician power (tribunicia potestas) and control in the East,
 all of which mirrored positions that Agrippa had previously held. However, despite these successes and despite his advancement, Tiberius was not happy.
Retirement to Rhodes (6 BC)
Remnants of Tiberius' villa at
, on the coast midway between Rome and Naples
In 6 BC, on the verge of accepting command in the East and becoming the second most powerful man in Rome, Tiberius suddenly announced his withdrawal from politics and retired to
 The precise motives for Tiberius's withdrawal are unclear.
 Historians have speculated a connection with the fact that Augustus had adopted Julia's sons by Agrippa
Lucius, and seemed to be moving them along the same political path that both Tiberius and Drusus had trodden.
Tiberius's move thus seemed to be an interim solution: he would hold power only until his stepsons would come of age, and then be swept aside. The promiscuous, and very public, behavior of his unhappily married wife, Julia,
 may have also played a part.
Tacitus calls it Tiberius' intima causa, his innermost reason for departing for Rhodes, and seems to ascribe the entire move to a hatred of Julia and a longing for Vipsania.
 Tiberius had found himself married to a woman he loathed, who publicly humiliated him with nighttime escapades in the
Roman Forum, and forbidden to see the woman he had loved.
Whatever Tiberius's motives, the withdrawal was almost disastrous for Augustus's succession plans. Gaius and Lucius were still in their early teens, and Augustus, now 57 years old, had no immediate successor. There was no longer a guarantee of a peaceful transfer of power after Augustus's death, nor a guarantee that his family, and therefore his family's allies, would continue to hold power should the position of
Somewhat apocryphal stories tell of Augustus pleading with Tiberius to stay, even going so far as to stage a serious illness.
 Tiberius's response was to anchor off the shore of
Ostia until word came that Augustus had survived, then sailing straightway for Rhodes.
 Tiberius reportedly regretted his departure and requested to return to Rome several times, but each time Augustus refused his requests.
Heir to Augustus
With Tiberius's departure, succession rested solely on Augustus' two young grandsons, Lucius and Gaius Caesar. The situation became more precarious in AD 2 with the death of Lucius. Augustus, with perhaps some pressure from Livia, allowed Tiberius to return to Rome as a private citizen and nothing more.
 In AD 4, Gaius was killed in
Armenia, and Augustus had no other choice but to turn to Tiberius.
The death of Gaius in AD 4 initiated a flurry of activity in the household of Augustus. Tiberius was adopted as full son and heir and in turn, he was required to adopt his nephew,
Germanicus, the son of his brother Drusus and Augustus' niece
 Along with his adoption, Tiberius received tribunician power as well as a share of Augustus's maius imperium, something that even Marcus Agrippa may never have had.
In AD 7,
Agrippa Postumus, a younger brother of Gaius and Lucius, was disowned by Augustus and banished to the island of
Pianosa, to live in solitary confinement.
 Thus, when in AD 13, the powers held by Tiberius were made equal, rather than second, to Augustus's own powers, he was for all intents and purposes a "co-princeps" with Augustus, and in the event of the latter's passing, would simply continue to rule without an
interregnum or possible upheaval.
However, according to
Suetonius, after a two-year stint in
Germania, which lasted from 10−12 AD,
 "Tiberius' returned and celebrated the triumph which he had postponed, accompanied also by his generals, for whom he had obtained the triumphal regalia. And before turning to enter the Capitol, he dismounted from his chariot and fell at the knees of his father, who was presiding over the ceremonies.”
 "Since the consuls caused a law to be passed soon after this that he should govern the provinces jointly with Augustus and hold the census with him, he set out for
Illyricum on the conclusion of the lustral ceremonies."
Thus according to Suetonius, these ceremonies and the declaration of his "co-princeps" took place in the year 12 AD, after Tiberius' return from Germania.
 "But he was at once recalled, and finding Augustus in his last illness but still alive, he spent an entire day with him in private."
 Augustus died in AD 14, at the age of 75.
 He was buried with all due ceremony and, as had been arranged beforehand,
deified, his will read, and Tiberius confirmed as his sole surviving heir.