Orhan Gazi was born in 1281 in Sogut. His father was Osman Gazi and his mother was Malhun Sultana, the daughter of Omer, who was a respected person in the Kayi Clan. Orhan Gazi was tall, had a blonde beard and blue eyes. He was a benign, forgiving, religious and fair ruler. He admired the theologians. He had strong and patient character. He spent most of his time with his people or by visiting them. He had won the admire of his people in a short time.
He minted silver coins in his own name which were called as "Akçe" in Turkish. He was known for his charitable acts, distributing great amounts of his wealth to the poor and passing time with the common people to hear their thoughts and complaints. His nickname, Gazi, comes from the fact that he fought many "Gaza"s, known as the "Holly Wars". He married Holofira, a Byzantine noble woman, and changed her name to Nilufer Hatun after converting her to Islam. From this marriage the next sultan, Murad Hüdavendigar (Murad I), was born.
Like his father, Orhan conducted many battles all through his life and conquered many lands. In 1326 he captured Bursa and made it capital of his empire. Then he captured Iznik in 1330, Murdunu in 1331, Gemlik in 1333, Izmit in 1337, Ankara and Gallipoli-Dardenelles in 1354, and extended the Ottoman Empire to the Asian shores of the Bosphorus in 1352 as well as in Thrace.
He made his brother, Allaedin Pasha, his Grand Vizier. In 1359 he stepped down leaving the throne to his son, Murat I and retired himself to Bursa until he died in 1368.