This article explores Ovid's Heroides 15 (the Epistula Sapphus) through a post-human feminist approach, engaging with the most recent scholarly debate on (Ovid's) Sappho's polysemous poetic language, polyphonic narrative, and gender fluidity. Drawing from recently published works that explore the intersections between posthumanism and antiquity, I show that Her. 15 is resituated within the 'posthuman turn' and accordingly reinterpreted as an expression of Ovid's and Sappho's poetic identity. Sappho's self-identification with her polymorphic poetry, assimilation into the natural world, and transitional sexual identity serve to both downplay and destabilize her role as a poetic subject, while at the same time enhancing her (and Ovid's) poetic creation. The idea of poetry as a self-shaping force is articulated by the agency that certain poetic objects (e.g., the letter, the poem, the verses), as well as other animate or inanimate natural elements (e.g., the branches and birds), hold within the epistle. Ovid has Sappho forego her poetic agency and question her literary skills; however, her poetic identity is also reaffirmed and strengthened precisely by the composition of her epistle. The displacement of the 'human' poet thus serves to enhance the centrality of the artistic, literary work. This dialectic between the limits of Sappho as a poet and the boundlessness of her poetry persists until—and reaches its peak at—the end of Her. 15, where Sappho anticipates her self-murder. Her (foretold) leap in the waters of the Leucadian Sea (217–220) can be interpreted both as a form of self-annihilation and as a means of stressing the permanence and timelessness of her own and Ovid's poetic talents.