The precise details of the author's life cannot be securely reconstructed based on presently available evidence. The Vita Iuvenalis (Life of Juvenal), a biography of the author that became associated with his manuscripts no later than the 10th century, is little or nothing more than extrapolation from the Satires themselves.

The traditional biographies, including the Vita Iuvenalis, give us the writer's full name, and also tell us that he was either the son or adopted son of a rich freedman. He is supposed to have been a pupil of Quintillian, and to have practised rhetoric until he was middle-aged, both as amusement and for legal purposes (the Satires make both frequent and accurate references to the operation of the Roman legal system). His career as a satirist is supposed to have begun at a fairly late stage in his life.

The biographies agree in giving his birthplace as Aquinum, and also agree in allotting to his life a period of exile due to insulting an actor with high levels of court influence: the emperor who banished him is given as either Trajan or Domitian, and all the biographies place his exile in Egypt, with the exception of one that opts for Scotland.

Only one of these traditional biographies supplies a date of birth for Juvenal: it gives 55 AD, which is most probably guesswork but accords reasonably well with the rest of the evidence. Other traditions have him surviving for some time past the year of Hadrian's death (138 AD). Some sources place this death in exile, others have him being recalled to Rome (the latter of which is considered more plausible by contemporary scholarship). If he was exiled by Domitian, it is then possible that he was one of the political exiles recalled during the brief reign of Nerva.

It is impossible to tell how much of the content of these traditional biographies is fiction and how much is fact. Large parts are clearly mere deduction from Juvenal's writings, but some elements appear more substantial. Juvenal never mentions a period of exile in his life, yet it appears in every extant traditional biography. Many scholars think the idea a later invention; the Satires do display some knowledge of Egypt and Britain, and it is thought that this gave rise to the tradition that Juvenal was exiled. Others, however - particularly Gilbert Highet - regard the exile as factual, and these scholars also supply a concrete date for the exile: 93 AD until 96, when Nerva became Emperor. They argue that a reference to Juvenal in one of Martial's poems, which is dated to 92, is impossible if at this stage Juvenal was already in exile or had served his time in exile, since Martial would not have wished to antagonise Domitian by mentioning such a persona non grata as Juvenal. If Juvenal was exiled, he would have lost his patrimony, and this may explain the consistent descriptions of the life of the client he bemoans in the Satires.

The only other available piece of biographical evidence is the following 19th-century dedicatory inscription, said to have been found at Aquinum with the text:

...]RI·SACRVM

...]NIVS·IVVENALIS

...] COH·[.]·DELMATARVM

II·VIR·QVINQ·FLAMEN

DIVI·VESPASIANI

VOVIT·DEDICAV[...]UE

SVA PEC

CERE]RI·SACRVM

D(ECIMVS) IV]NIVS·IVVENALIS

TRIB(VNVS)] COH(ORTIS)·[I]·DELMATARVM

II·VIR·QVINQ(VENNALIS)·FLAMEN

DIVI·VESPASIANI

VOVIT·DEDICAV[ITQ]UE

SVA PEC(VNIA)

To Ceres (this) sacred (thing)

(Decimus Junius?) Juvenalis

military tribune of the 1st cohort of the Dalmatian (legions)

Duovir, Quinquennalis, Flamen

of the Divine Vespasian

vowed and dedicated

at his own expense

(Corpus Inscriptionum Latinarum X.5382)

Scholars are usually of the opinion that this inscription does not relate to the poet himself: a military career would not fit well with the pronounced anti-militarism of the Satires, and moreover the Dalmatian legions do not seem to have existed prior to 166 AD. Therefore, however, it seems likely that this Juvenal was a later relative of the poet, as they both came from Aquinum and were associated with the goddess Ceres (the only deity the Satires shows much respect for). But if the theory that connects the two Juvenals is right, then the inscription does show that Juvenal's family was reasonably wealthy, and that if the poet really was the son of a foreign freedman, then his descendants assimilated themselves into the Roman class structure quickly. Green thinks it more likely that the tradition of the freedman father is false, and that Juvenal's ancestors were minor nobility of Roman Italy of relatively ancient descent.

Juvenal is credited with sixteen known poems divided between five books; all are in the Roman genre of Satire, which, at its most basic in the time of the author, comprised a wide-ranging discussion of society and social mores in dactylic hexameter. In Satire I, concerning the scope and content of his work, Juvenal says:

Back from when Deucalion climbed a mountain in a boat

as the clouds lifted the waters, and then asked for an oracle,

and then little by little spirit warmed the soft stones

and Pyrrha showed naked girls to their husbands,

whatever men do — prayer, fear, rage, pleasure

joy, running about — is the grist of my little book.

ex quo Deucalion nimbis tollentibus aequor

nauigio montem ascendit sortesque poposcit

paulatimque anima caluerunt mollia saxa

et maribus nudas ostendit Pyrrha puellas,

quidquid agunt homines, uotum, timor, ira, uoluptas,

gaudia, discursus, nostri farrago libelli est.

(1.81-86)

Juvenal claims as his purview the entire gamut of human experience since the dawn of history. Quintilian — in the context of a discussion of literary genres appropriate for an oratorical education - claimed that, unlike so many literary and artistic forms adopted from Greek models, “satire at least is all ours” (satura quidem tota nostra est). At least in the view of Quintillian, earlier Greek satiric verse (e.g. that of Hipponax) or even Latin satiric prose (e.g. that of Petronius) did not constitute satura per se. Roman Satura was a formal literary genre rather than being simply clever, humorous critique in no particular format.

• Book I: Satires 1-5
• Book II: Satire 6
• Book III: Satires 7-9
• Book IV: Satires 10-12
• Book V: Satires 13-16 (Satire 16 is incompletely preserved)

The individual Satires (excluding Satire 16) range in length from 130 (Satire 12) to c. 695 (Satire 6) lines. The poems are not individually titled, but translators have often added titles for the convenience of readers.

Although Juvenal has enjoyed a wide readership across the centuries, the Roman world view found in the content and tone of the Satires is criticized today in some quarters for its incompatibility with present-day liberal social-political ideology ... that of feminism, anti-xenophobia, and class equality.

While Juvenal's mode of satire has been noted from antiquity for its wrathful scorn towards all representatives of social deviance, some politically progressive scholars such as W.S. Anderson and later S.M. Braund have attempted to defend his work as actually a rhetorical persona (mask) taken up by the author to critique the very attitudes he appears to be exhibiting in his works.

In any case it would be an error to read the Satires as a literal account of normal Roman life and thought in the late 1st and early 2nd centuries AD, just as it would be an error to give credence to every slander recorded in Tacitus or Suetonius against the members of prior imperial dynasties. Themes similar to those of the Satires are present in authors spanning the period of the late Roman Republic and early Empire ranging from Cicero and Catullus to Martial and Tacitus; similarly, the stylistics of Juvenal’s text fall within the range of post-Augustan literature as represented by Persius, Statius, and Petronius. Certainly the Satires represent only the world view of a portion of the Roman population, not speaking of the concerns of women, immigrants, slaves, children, or men not of the elite, educated audience addressed by the author.

With these caveats, it is nonetheless possible to approach the Satires as a helpful source for studying the culture of early Imperial Rome. In addition to a wealth of incidental information on everything from diet to décor, the Juvenal's work reveals what is most essential to a civilization: the issues at the core of the identity of a society such as Rome.

The Satires have inspired many authors, including Samuel Johnson, who modeled his “London” on Satire III and his “Vanity of Human Wishes” on Satire X. Juvenal also helped come up with the name for a forensically important beetle, Histeridae. Juvenal is the source of many well-known maxims, including:

• that the common people...rather than caring about their freedom...are only interested in “bread and circuses” (panem et circenses 10.81; i.e. food and entertainment),
• that...rather than for wealth, power, or children...men should pray for a “sound mind in a sound body” (mens sana in corpore sano 10.356),
• that a perfect wife is a “rare bird” (rara avis in terris nigroque simillima cycno 6.165; a rare bird in the earth and most similar to a black swan)
• and the troubling question of who can be trusted with power...“who will watch the watchers?” or "who will guard the guardians themselves?" (quis custodiet ipsos custodes 6.347-48).