The Epistulae ([ɛˈpɪs.t̪ʊ.ɫ̪ae̯], "letters") are a series of personal missives by Pliny the Younger directed to his friends and associates. These Latin letters are a unique testimony of Roman administrative history and everyday life in the 1st century. The style is very different from that in the Panegyricus, and some commentators maintain that Pliny initiated a new genre: the letter written for publication. This genre offers a different type of record than the more usual history; one that dispenses with objectivity but is no less valuable for it. Especially noteworthy among the letters are two in which he describes the eruption of Mount Vesuvius in 79 during which his uncle Pliny the Elder died (Epistulae VI.16, VI.20), and one in which he asks the Emperor for instructions regarding official policy concerning Christians (Epistulae X.96).
The Epistulae are usually treated as two halves: those in Books 1 to 9, which Pliny prepared for publication; and those in Book 10, which were written to or from the Emperor Trajan, and which were copied from the imperial archives. Pliny is not thought to have any influence in the selection of the letters in this book. The greater share of the letters in book 10 concern Pliny's governorship of Bithynia-Pontus.
Other major literary figures of the late 1st century AD appear in the collection as friends or acquaintances of Pliny's, e. g. the poet Martial, the historian Tacitus and the biographer Suetonius. However, arguably the most famous literary figure to appear in Pliny's letters is his uncle. His nephew provides details of how his uncle worked tirelessly to finish his magnum opus, the Historia Naturalis (Natural History). As heir to his uncle's estate, Pliny the Younger inherited the Elder's large library, benefiting from the acquisition.