The mosque was built between 1396 and 1400, during the time of Yıldırım Beyazıt, in a large area where the Orhan Gazi park is located. Among the Ottoman mosques, it is the first one to be a monumental building with several domes. The Ulu Mosque has 20 domes on twelve large quadrangular piers. After the 1396 Niğbolu victory of Yıldırım Beyazid, the Great Mosque was started to be built. After the completion of the construction, the first prayers where Yıldırım Beyazid, Mullah Fenari and Emir Sultan were present was made by Somuncu Baba. Ulucami's first imam, the writer of Mevlid, was Süleyman Çelebi. Inside the mosque, the fountain located under the dome has a sixteen-angular pool and three bowls.
The inscription on the Mimbar gate shows the finishing date of the mosque as 802 (1399-1400). The first of the two minarets of the mosque situated in the west was built by Yıldırım Beyazid and the minaret in the east was built by Sultan Mehmed Çelebi. The mosque, which had been destroyed by the Tymurite invasion, was repaired during these years and the biggest repairs were made after the earthquake of 1855. Source : Bursa Provincial Directorate of Culture and Tourism