The Schleswig-Holsteinisches Sinfonieorchester is the resident orchestra of the Schleswig-Holsteinisches Landestheater, Germany's largest regional theatre company, based in Rendsburg with regular performances in Flensburg, Schleswig and other towns across the German-Danish border region. Its roots go back to 1920, when military musicians in Flensburg formed an ensemble that later became the Nordmark-Sinfonie-Orchester. Since the 2024/2025 season the Malaysian-German conductor Harish Shankar has served as music director, and the orchestra holds an annual joint concert with the Danish Sønderjyllands Symfoniorkester.
The orchestra held its annual collaboration concert with Sønderjyllands Symfoniorkester under the title "Titanerne" on June 3 in Flensburg and June 4 in Alsion, Sønderborg, with Harish Shankar as conductor.
In a portrait from October 2025, it is emphasized that the audience numbers at the orchestra's symphony concerts have been increasing under GMD Harish Shankar's leadership.
It was announced in June 2023 that conductor Harish Shankar will become the new general music director for the orchestra and the state theatre from the 2024/2025 season.
