Musa Çelebi (died 5 July 1413) was an Ottoman prince () and a co-ruler of the empire for three years during the Ottoman Interregnum. Background Musa was one of the sons of Bayezid I, the fourth Ottoman sultan. There is no consensus about his mother's origin; she was either the daughter of the bey of the Turkish Germiyanids or a Byzantine princess. After the Battle of Ankara, in which Bayezid I was defeated by Tamerlane, Musa and Bayezıd were taken prisoners of war by Tamerlane. However, after Bayezıd's death in 1403, he was released. He returned to the Ottoman Empire, which was now in turmoil, and tried to access the throne in Bursa, the Anatolian capital of the empire in 1403. However, three of his brothers were also claimants to the Ottoman throne: İsa Çelebi in Balıkesir and Mehmet Çelebi in Amasya (both in the Anatolian portion of the empire), Süleyman Çelebi in Edirne, the Rumeli (European) capital. (the Ottoman Empire at the time had two capitals, since the declining Byzantine Empire in Constantinople separated the two parts of the Ottoman lands). Ottoman Interregnum İsa defeated Musa and captured Bursa. Musa took refuge in Germiyanid territory, where he waited for a suitable moment to try again. In 1406, Mehmet, who had defeated İsa, became the sole ruler of the Anatolian portion of the empire, but he was no match for Süleyman of the Rumeli (European) portion. Mehmet and Musa met in Kırşehir in central Anatolia and formed an alliance against Süleyman. Most of the beyliks in Anatolia also supported this alliance. According to the terms of the alliance, Musa was transferred to the European part over the Black Sea where he allied himself with Mircea of Wallachia. Süleyman now had to fight on two fronts, against Mehmet in Anatolia and against Musa in Europe. This strategy was partially successful, as Süleyman gave up his hopes to conquer the Anatolian portion of the empire. However, he was able to defeat Musa at the battles of Kosmidion and Edirne. Despite his defeat, Musa continued with hit-and-run tactics against Süleyman up until 1410. Meanwhile, Süleyman had lost most of his previous allies due to his uncontrollable temper. In 1411, Musa's tactics finally gave victory and he captured Edirne. The defeated Süleyman, while attempting to escape into Byzantine territories, was killed by villagers on 18 February 1411, and Musa found himself as the co-sultan