Born in Reykjavík, Iceland, dramatic soprano Agnes Thorsteins began her musical journey at a young age, initially studying piano at the Garðabær Music School. Her passion for the voice soon emerged, leading her to vocal studies under the guidance of Guðrún Jóhanna Jónsdóttir. By the age of 18, she had completed her formal training in both disciplines.
Agnes pursued her higher education at the University of Music and Performing Arts in Vienna, studying with Prof. Anton Scharinger and later with Prof. Regine Köbler, earning her Bachelor's degree with distinction in 2016. 

Her development was further enriched through masterclasses with celebrated artists including Prof. Dunja Vejzović, Anne Sofie von Otter, and Dame Kiri Te Kanawa. She continued her operatic training in the masterclass program of Univ.-Prof. Beverly Blankenship and Univ.-Prof. Peter Marschik in 2019. A frequent performer at the Schönbrunn Palace Theater in Vienna, she appeared over three consecutive seasons in productions of Le Nozze di Figaro, portraying both Marcellina and Cherubino.
Her early promise was recognized with scholarships from the Arts and Culture Council of Kópavogur (2010) and the Marino Pétursson Foundation (2016). 

From 2016 to 2018, Agnes was a member of the Niederrhein Opera Studio, where she brought to life a wide array of roles including Hänsel (Hänsel und Gretel), Lola (Cavalleria Rusticana), and Orfeo (Orfeo ed Euridice).
Following her time at the studio, she began working with esteemed vocal coach Neil Semer, performing extensively in concerts and guest engagements across Iceland and Europe.

Under the mentorship of KS Prof. Dunja Vejzović, Agnes transitioned to the dramatic soprano repertoire—a pivotal evolution that continues to shape her artistic trajectory. Her voice, marked by both power and lyricism, has since found a natural home in the works of Richard Wagner and Pyotr Ilyich Tchaikovsky.
In June 2023, she made both her role and house début as Liza in Pikovaya Dama at the Croatian National Theatre in Rijeka.
The following season marked her Wagnerian début as Senta in Der fliegende Holländer at the Theaters of Mönchengladbach and Krefeld.
In February 2025, she gave her much-anticipated début as Brünnhilde in Ring an einem Abend at Theater Koblenz, under the baton of Marcus Merkel. 

Now based in Vienna, Agnes continues to refine her artistry in collaboration with the distinguished Polish vocal coach and pianist Marcin Kozieł. Her performances across Europe have been lauded for their vocal richness, dramatic intensity, and deep emotional resonance. Recent highlights include her interpretations of Brünnhilde and Senta, roles that showcase her profound connection to the music of Richard Wagner.