My D.Phil, dissertation sheds new light on German literary decadence around 1900, its universal concepts, plurality of discourses and poetic transformations. The heuristic value of my dissertation is a refined differentiation of Dekadenz which reconstructs the literary history of the concept and for the first time proposes specific poetic constellations. In chapter 1, decadence is reviewed with its rich research heritage and introduced as a decisive concept and discourse of aesthetic modernism. Although much has been written on decadence, the concept is clearly in need of scholarly reconsideration. I argue that decadence is not only a vague epochal construct and an ensemble of motifs, but also encompasses discourses, universal concepts and a versatile literary style. In view of the stylistic eclecticism around 1900, I argue that decadence is a dynamic and malleable concept which can be combined with other aesthetic styles, movements and philosophical contexts depending on the specific author. Chapter 2 contextualizes Dekadenz from its etymology and central discourses to its universal concepts. Etymologically derived from the Latin verb de-cadere decadence signifies a downward movement and a figure of fragmentation. It evokes cultural and political decline especially that of the Roman Empire (décadence romaine) and undergoes various aesthetic transformations (1857-1894). After touching upon the precursors Baudelaire (1857), Bourget (1883) and Bahr (1889-1894), I dwell on Nietzsche to demonstrate the philosophically complex German double evaluation of decadence. I derive three universal concepts from Nietzsche (health vs. sickness, endings vs. new beginnings, fragmentation vs. wholeness) which are crucial to my literary analysis. My comprehensive literary analysis centers on three specific poetic constellations of decadence between late realism and aesthetic modernism. Chapter 3 illuminates Mann's spätrealistische Dekadenz (1894-1924) with his (Nietzschean) double evaluations. Transformations of decadence are shown in his early novellas, Buddenbrooks, Der Tod in Venedig and Der Zauberberg. Chapter 4 illustrates Hofmannsthal's ästhetizistische Dekadenz (1891-1902) in his early essays, his prose fragment Age of Innocence and Das Märchen der 672. Nacht. A significant transformation of decadence is illuminated in Ein Brief (1902), where Nietzschean decadence is concentrated and tentatively overturned. In chapter 5, Rilke's modernistische Dekadenz (1898-1910) is shown from his early fragment Ewald Tragy to his only novel Die Aufzeichnungen des Malte Laurids Brigge. His novel attempts a poetic 'revaluation of all values' and culminates in the emergence of a genuinely modernist decadence.