At the start of the twentieth century, East Asian literature was in a state of flux. Korean intellectuals, like their counterparts in China and Japan, began a collective effort to renew their literature, moving toward forms of writing that more closely approximated everyday language. Scholars of this period have long debated how this transition took place. It is widely accepted that the push toward vernacularization was inspired by Western literature, which was understood to be modern in comparison to past traditions that had been largely drawn from classical Chinese models. Many researchers have identified the integral role of translation in this process as a tool used to import the latest literary trends. My research reframes translation as a fundamentally generative process that enabled writers to conceive new literary forms that did not previously exist in their own language. The dissertation also demonstrates how the multilingual environment of colonial Korea spurred experimentation in writing across several languages, contributing to the development of new literary practices. My project examines the interplay between translation and the formation of modern Korean literature in relation to the emergence of vernacular poetry during the 1920s. Through close readings of translations, critical writing, and original poetry in Korean and Japanese, I unearth the creative process of early Korean intellectuals, who sought to invent a new form of writing. When viewed from their perspective, the literary translation of this decade is revealed to be a medium in which writers freely experimented with language, not a process intended to produce faithful replicas of foreign texts. The dissertation is divided into five constituent parts: an introduction, conclusion, and three body chapters that each explore a different aspect of how translation shaped original writing. Chapter One, “Writing in Translation: Kim Ŏk and the Emergence of the Vernacular Poem,” focuses on Kim Ŏk, one of the first prominent Korean translators of foreign poetry. The chapter illustrates how Kim extensively reused language from his translations when composing original poetry, yielding a model of vernacular poetry that was widely adopted in the 1920s. Chapter Two, “Translating Romance: Reading Han Yong-un,” is centered around Han Yong-un, a Buddhist monk who published the celebrated poetry collection The Silence of Love (Nim ŭi ch’immuk) in 1926. I argue that Han’s poetic style was informed by an intellectual environment of mass translation, which enabled the circulation of competing discourses of love. My analysis shows how Han encouraged his readers to embrace multiple interpretations, each based on a different discourse, thereby engendering a new way to read poetry that also suggested the makings of a national community unified in the 1920s by a collective sense of absence. My final chapter, “Translating Rhythm: Chŏng Chi-yong and the Development of Free Verse,” examines the early career of Chŏng Chi-yong, one of Korea’s preeminent modernist poets. The chapter contends that by writing in both Japanese and Korean in the late 1920s, and translating his own poetry between the two, Chŏng developed a new method of free verse rhythm that was disentangled from the soundscape of any single language. In analyzing these three individual cases, the dissertation concretely demonstrates the myriad ways in which literary translation was enmeshed with the formation of modern Korean literature. More specifically, I show how the creation of modern Korean poetry involved the efforts of intellectuals who were reading and writing in foreign languages, their experiences with translation influencing their original output. By tracing developments in writing on the level of language, the dissertation unearths the historical origins of seemingly-timeless notions about what constitutes Korean literature in the linguistic experimentation afforded by translation. Using Korea as a telling example, my research illustrates how ostensibly closed traditions of national literatures in East Asia changed in the early twentieth century, their transformations precipitated by actors working in multiples languages.