The flag is known as the Black Standard of Muhammad. There are many variants of the flag, and as far as I can tell the variant used by ISIS is original, but other variants have been used by many groups before.
The flag can either be a pure black flag, or it may have the Shahada ("There is no god but Allah. Muhammad is the messenger of Allah.") printed on it in white.
- A pure black flag was used by the Abassid Caliphate from the 8th century through the 16th, the Hotaki Empire in the 18th century, and Afghanistan in the late 19th century.
- An inverted Black Standard wasis used by the Taliban.
- Several different variants have been used by modern Islamist and jihadist groups, including al-Qaeda, al-Shabaab, and the Islamic Courts Union.
- And a variant of the flag is used by ISIL.