The Sancak-ı Şerif (Turkish, Ottoman (1500-1928);: سنجاق شريف|lit=great flag) is the alleged original standard of the Islamic prophet Muhammad. It is kept along with other relics of Muhammad, in the treasury of the Topkapı Palace, in Istanbul.
According to legend, the flag was used in the first Muslim wars; then passed into the hands of the Umayyads and Abbasids; and finally, with Selim I's conquest of Egypt in 1517, fell into Ottoman hands. The Ottomans carried the flag into battle, beginning with their Hungarian campaign circa 1521.
According to Ottoman historian Silahdar Findiklili Mehmed Agha (d. 1727), the flag was made of black wool.
It was believed that if the Ottoman state, or Islam generally, were threatened with extreme danger, the flag should be taken into the field by the Ottoman sultan personally, whereupon every Muslim capable of taking arms must rally under the flag.