Olgun Şimşek was born in the village of Yenice in Büyükorhan, Bursa. His father was a primary school teacher and his mother was a housewife. He graduated in theatre from the Istanbul University State Conservatory and began acting professionally in 1993.
Şimşek acted in the play Otogargara with Demet Akbağ and Yilmaz Erdogan. He had a small parts in the films Tersine Dünya in 1993 and Yer Çekimli Aşıklar in 1995 . In 1998, he acted in the film Karışık Pizza for which he won the Most Promising Actor award at the Ankara Film Festival.
Şimşek also had appearances in television series such as Sihirli Ceket, Yedi Numara, Beşik Kertmesi ve Alacakaranlık. In 2004, he starred in the film Yazı Tura directed by Uğur Yücel where he played a disabled soldier. For this, he won several awards including the Golden Orange for Best Actor as well as Best Actor awards at the Ankara Film Festival, İstanbul Film Festival, Adana Golden Coccoon Festival and the SİYAD awards. Currently, he is starring in a Turkish comedy show "Yalan Dunya'.