Gustav Mahler's music has been extensively studied and discussed in both scholarly and popular circles, especially since the middle of the past century. His conducting and directorial activity, however, deserves greater attention. The 1903 Vienna Court Opera production of Richard Wagner's "Tristan und Isolde" was a landmark in opera history because of Mahler's masterful conducting and Secession artist Alfred Roller's vibrant costumes, sets, and lighting design. Roller helped to move the Court Opera away from overly naturalistic and museum-like stage sets and costumes towards greater stylization and abstraction. The dissertation situates this collaborative project within fin-de-siecle debates about the nature of the Wagnerian Gesamtkunstwerk, which today is generally misinterpreted as a multimedia spectacle in which all production elements are conceived organically. Previous studies of this production explored the technical achievements of Mahler and Roller and surveyed the critical response in Vienna. More work remains to be done in examining the deeper cultural significance of the Mahler-Roller "Tristan" and differing contemporary views on the proper balance of aural and visual stimuli in the Gesamtkunstwerk. This study demonstrates the degree to which Mahler participated in a long tradition of addressing the proper sphere of the arts in the theatrical spectacle through his work with Roller in Vienna. Their partnership also anticipated the spirit of cooperation and mutual encouragement that characterized the work of influential troupes such as the Ballets Russes and Ballets Suedois, both of which represented the "modern" in the twenty years after Mahler's death. The spirit of the Mahler-Roller production of "Tristan und Isolde" can also be detected in Wieland Wagner's bold postwar productions at Bayreuth. Through his work with Roller, Mahler served as a link between naturalistic Romantic stage practice, epitomized by many nineteenth-century Wagner productions, and the more symbolic style of twentieth-century directors such as Wieland Wagner.