Orhan I or Orhan Bey was the second bey of the nascent Ottoman Empire (then known as the Ottoman Beylik or Emirate) from 1326 to 1359. He was the son of Osman I and Malhun Hatun, the daughter of Abdulaziz Bey.
In the early stages of his reign, Orhan focused his energies on conquering most of northwestern Anatolia. The majority of these areas were under Byzantine rule and he won his first battle, at Pelekanon, against the Byzantine Emperor Andronikos III Palaiologos. Orhan also occupied the lands of the Karasids of Balikesir and the Ahis of Ankara.
A series of civil wars surrounding the ascension of the nine-year-old emperor John V benefited Orhan greatly. In the first, the regent John Kantakouzenos married his daughter Theodora to Orhan and employed Ottoman warriors against the rival forces of the queen dowager, allowing them to loot Thrace. In the second, Kantakouzenos used Ottoman forces against John V himself, granting them the use of a European fortress at Çimpe around 1352. A major earthquake devastated Gallipoli (modern Gelibolu) two years later and Orhan's son Suleyman Pasha occupied the town, giving the Ottomans a strong bridgehead into mainland Europe.