Kostja Ullmann (born 30 May 1984) is a German actor, best known for his leading role in the award-winning coming-of-age drama Sommersturm (Summer Storm), which gained a lot of praise throughout Europe.

Ullmann was born in Hamburg to a German father and an Indian mother. He entered the stage at the age of eleven and performed at Hamburg's Ernst Deutsch Theater and Winterhuder Fährhaus. In 1998, he made his TV debut in a minor part in the crime series Alphateam.