Her international career began after she appeared at the Vienna State Opera in 1965 in two leading roles, Ortrud in Wagner Lohengrin and Eboli in Verdi's Don Carlos.

In 1960 she made her debut at the Hamburg State Opera and the Bayreuth Festival, where she performed until 1979 and was gradually assigned larger roles, culminating in Ortrud in Lohengrin, opposite Peter Hofmann and Karan Armstrong.

[1] Hesse made her Royal Opera House debut in 1969 as the Nurse in Richard Strauss's Die Frau ohne Schatten.

[5] In 1972, she appeared at the Paris Opéra Garnier in Mozart's Le nozze di Figaro, and again as the Nurse,[1][2] In 1974 and 1975 she was the Nurse in an acclaimed production at the Salzburg Festival, conducted by Karl Böhm and directed by Günther Rennert, alongside James King and Leonie Rysanek as the imperial couple and Walter Berry and Birgit Nilsson as the Dyer and his wife,[2][6] in a production that was recorded.

[1] Hesse was a regular guest at the Vienna State Opera from 1965 to 1988, where she appeared as Herodias, the Nurse, Ortrud, Brangäne, Magdalene, Fricka and Waltraute, Eboli, as well as Amneris in Verdi's Aida, Azucena in his Il trovatore, Maddalena in his Rigoletto and Preziosilla in his La forza del destino, Giulietta in Offenbach's Les contes d'Hoffmann and Burija in Janáček's Jenůfa.

They had met in 1975 at the Salzburg Festival where she appeared in Die Frau ohne Schatten and he served as an assistant to the production's set designer, Günther Schneider-Siemssen.

[4][11] Bartók: Bizet: Gluck: Hindemith: Humperdinck: Janáček: Korngold: Mozart: Offenbach: Strauss: Stravinsky: Verdi: Wagner: Hesse performed on DVD as Mary in Wagner's Der fliegende Holländer, with Donald McIntyre in the title role, in 1965,[21] and as Brangäne in Tristan und Isolde (with Nilsson and Jon Vickers in 1973, filmed in the Roman Theatre of Orange.

Alan Blyth wrote in a review for Gramophone in 2004: "Ruth Hesse sings an ample-sounding Brangäne of a kind hardly heard today, and interprets the part with apt sympathy.