Wikipedia
The Heroides (The Heroines), or Epistulae Heroidum (Letters of Heroines), is a collection of fifteen epistolary poems composed by Ovid in Latin elegiac couplets and presented as though written by a selection of aggrieved heroines of Greek and Roman mythology in address to their heroic lovers who have in some way mistreated, neglected, or abandoned them. A further set of six poems—widely known as the Double Heroides and numbered 16 to 21 in modern scholarly editions—follows these individual letters and presents three separate exchanges of paired epistles: one each from a heroic lover to his absent beloved and from the heroine in return.
Arguably some of Ovid's most influential works (see below), one point that has greatly contributed to the mystique of the Heroides—and to the reverberations they have produced within the writings of later generations—is directly attributable to Ovid himself. In the third book of his Ars Amatoria, Ovid makes the claim that, in writing these fictional epistolary poems in the personae of famous heroines—rather than from a first-person perspective—he created an entirely new literary genre. Recommending parts of his poetic output as suitable reading material to his assumed audience of Roman women, Ovid wrote of his Heroides: "vel tibi composita cantetur Epistola voce: | ignotum hoc aliis ille novavit opus" (Ars Amatoria 3.345–6: "Or let an Epistle be sung out by you in practiced voice: unknown to others, he [ sc. Ovid] originated this sort of composition”). The full extent of Ovid's originality in this matter has been a point of scholarly contention: E. J. Kenney, for instance, notes that "novavit is ambiguous: either 'invented' or 'renewed', cunningly obscuring without explicitly disclaiming O[vid]'s debt to Propertius' Arethusa (4.3) for the original idea." In spite of various interpretations of Propertius 4.3, consensus nevertheless concedes to Ovid the lion's share of the credit in the thorough exploration of what was, in its time, a highly innovative poetic form.