The Mariinsky Theatre -- where Vladimir Shklyarov was the highest-ranking dancer -- confirmed the 39-year-old's death ... calling it a huge loss for the entire institution.

Russian state media outlet RIA Novosti reports authorities have launched an investigation into Shklyarov's death in St. Petersburg ... but according to the preliminary ruling, the fall was an accident.

Shklyarov’s tragic death came just 2 days before he was scheduled for complex spinal surgery ... with the Mariinsky Theatre and Russian media noting he had been on "serious painkillers" for a while.

Russian dancer Irina Baranovskaya said Shklyarov “went out onto the balcony to get some air and smoke,” and lost his balance on a narrow balcony, The Guardian reports.

Condolences poured in, with Diana Vishneva -- a fellow principal dancer at the Mariinsky -- calling his death a tragedy in an emotional IG tribute, while describing Shklyarov as the favorite partner of countless ballerinas.

Shklyarov’s talent was unmatched -- he graduated from the prestigious Vaganova Academy of Russian Ballet and dazzled in iconic productions like "Swan Lake," "Sleeping Beauty," "Romeo and Juliet," and "Don Quixote." His brilliance earned him the title of Honored Artist of Russia in 2020.

Shklyarov had been a vocal advocate for ending the war with Ukraine, from the time Russia invaded its neighbor in 2022.

Shklyarov was married to fellow Mariinsky dancer Maria Shirinkina, and together they shared 2 children.