Mehmed VI Vahideddin (Ottoman Turkish: ???? ??????? Me?med-i sâdis, ???? ?????? Vahideddin, Turkish: Vahideddin or Altinci Mehmet), who is also known as Sahbaba (meaning "Emperor-father") among his relatives, (14 January 1861 – 16 May 1926) was the 36th and last Sultan of the Ottoman Empire, reigning from July 4, 1918 until November 1, 1922 when the Ottoman Empire dissolved after World War I and became the nation of the Republic of Turkey on October 29, 1923.
The brother of Mehmed V, he became heir to the throne after the 1916 suicide of Abdülaziz's son Sehzade Yusuf Izzeddin as the eldest male member of the House of Osman.
He acceded to the throne after the death of Mehmed V.
He was girded with the Sword of Osman on 4 July 1918, as the thirty-sixth padishah.
His father was Sultan Abdulmejid I and mother was Gülüstü Hanim (1830 – 1865), an ethnic Abkhazian, daughter of Prince Tahir Bey Çaçba and his wife Afise Lakerba, originally named Fatma Çaçba.
Mehmed was removed from the throne when the Ottoman sultanate was abolished in 1922.