Mark Ćwiertnia, born on 11 January 1983, is better known as Mark Forster. He is a German singer, songwriter, and television personality, recognized for his albums Karton, Bauch und Kopf, and the project Eff. He has also worked with various artists and contributed to television projects. Forster served as a coach on The Voice of Germany from 2017 to 2022, guiding Anny Ogrezeanu to victory in 2022. He returned to the show as a coach in 2024, joining Samu Haber, Yvonne Catterfeld, and Kamrad.