Born in the small town of Venusia in the border region between Apulia and Lucania (Basilicata), Horace was the son of a freed slave, who owned a small farm in Venusia, and later moved to Rome to work as a coactor (a middleman between buyers and sellers at auctions, receiving 1% of the purchase price from each for his services). The elder Horace was able to spend considerable money on his son's education, accompanying him first to Rome for his primary education, and then sending him to Athens to study Greek and philosophy. The poet later expressed his gratitude in a tribute to his father:

If my character is flawed by a few minor faults, but is otherwise decent and moral, if you can point out only a few scattered blemishes on an otherwise immaculate surface, if no one can accuse me of greed, or of prurience, or of profligacy, if I live a virtuous life, free of defilement (pardon, for a moment, my self-praise), and if I am to my friends a good friend, my father deserves all the credit... As it is now, he deserves from me unstinting gratitude and praise. I could never be ashamed of such a father, nor do I feel any need, as many people do, to apologize for being a freedman's son. Satires 1.6.65–92

After the assassination of Julius Caesar, Horace joined the army, serving under the generalship of Brutus. He fought as a staff officer (tribunus militum) in the Battle of Philippi. Alluding to famous literary models, he later claimed that he saved himself by throwing away his shield and fleeing. When an amnesty was declared for those who had fought against the victorious Octavian (later Augustus), Horace returned to Italy, only to find his estate confiscated; his father likely having died by then. Horace claims that he was reduced to poverty. Nevertheless, he had the means to gain a profitable lifetime appointment as a scriba quaestorius, an official of the Treasury, which allowed him to practice his poetic art.

Horace was a member of a literary circle that included Virgil and Lucius Varius Rufus, who introduced him to Maecenas, friend and confidant of Augustus. Maecenas became his patron and close friend and presented Horace with an estate near Tibur in the Sabine Hills (contemporary Tivoli). Horace died in Rome a few months after the death of Maecenas at age 57. Upon his death bed, having no heirs, Horace relinquished his farm to his friend, the emperor Augustus, for imperial needs and it stands today as a spot of pilgrimage for his admirers.

Horace is generally considered to stand alongside Virgil and Ovid as one of the greatest poets of the Augustan Age. Several of his poetry's main themes, such as the beatus ille (an appraisal of simple life) and carpe diem (literally "pluck the day", more commonly rendered into English as "seize the day", but perhaps closer to "enjoy the day") were recovered during the late Middle Ages and the Renaissance, influencing poets such as Petrarch and Dante. However, those themes were not truly retaken till the 16th century, when the Renaissance culture and its admiration of Roman and Greek antiquity was solidly established. In that sense, the influence of Horace can be traced in the works of poets such as Garcilaso de la Vega, Juan Boscán, Torquato Tasso, Pierre de Ronsard and especially in Fray Luis de León. The latter wrote some of the most remarkable "Odes" dealing with the beatus ille precepts. Besides, several latter poets such as Shakespeare and Quevedo were heavily influenced by Horace's poetry. Moreover, his work Ars Poetica remained as a canonical guide for composing poetry till the end of romanticism, and it was known and studied by most writers; even though its precepts were not always thoroughly followed, it held an unimpaired prestige when it came to deal with the form, wording and setting of any poem, play or prose work, and its influence can be traced well into the works of playwrights and writers such as Lope de Vega, Michel de Montaigne, Henry Fielding, Calderón de la Barca, Pierre Corneille, Samuel Johnson, Goethe, Voltaire or Diderot.

Apart from carpe diem, Horace is also known for having coined many other Latin phrases that remain in use today, whether in Latin or translation, including Dulce et decorum est pro patria mori (It is sweet and fitting to die for one's country), Nunc est bibendum (Now we must drink), and aurea mediocritas ("golden mean").

Horace also forms the basis for the character Quintus Horatius Flaccus in the Oxford Latin Course, a Latin textbook for secondary students; the books loosely follow his life.

His works, like those of all but the earliest Latin poets, are written in Greek metres, ranging from the hexameters which were relatively easy to adapt into Latin to the more complex measures used in the Odes, such as alcaics and sapphics, which were sometimes a difficult fit for Latin structure and syntax.