Mehmed I Çelebi (nicknamed Kirisci, "the Executioneer") (died May 26, 1421) was a sultan of the Ottoman Empire. He was one of the sons of Beyazid I.

When Timur Lenk defeated the Ottomans in the Battle of Ankara and captured Beyazid, a civil war broke out in the empire, called the Ottoman Interregnum. Mehmed gained some lands in Anatolia, which at the time gave him access to the largest source of manpower in the Ottoman lands. Mehmed supported his brother Musa in the overthrow and murder of their eldest sibling, Suleiman of Rumelia in 1410. When Musa's harsh and arbitrary rule made enemies at home as well as abroad, Mehmed made an alliance with the Byzantine Emperor Manuel II Palaeologus. With access to the Dardanelles, Mehmed quickly overran Thrace and had Musa killed.

When Mehmed stood as victor in 1413 he crowned himself as sultan in Adrianople (Edirne). He restored the empire, moved the capitol from Bursa to Adrianople and conquered parts of Albania, the Turkish emirate Candaroglu and the Christian Kingdom of Cilicia. However, as part of the alliance, Mehmed recognized the Byzantine Emperor as his "father and overlord" and remained loyal to this anomaly — which must count as the last diplomatic triumph of the Eastern Roman Empire. Mehmed died in 1421.