Shamil Salmanovich Basayev (Russian: Шамиль Салманович Басаев; 14 January 1965 – 10 July 2006) was a Chechen militant Islamist and a leader of the Chechen rebel movement.

Starting as a field commander in the Transcaucasus, Basayev led guerrilla campaigns against Russian forces for years, as well as launching mass-hostage takings of civilians, with his goal being the withdrawal of Russian soldiers from Chechnya. Beginning in 2003, Basayev used the nom de guerre and title of Emir Abdallah Shamil Abu-Idris. In 1997–1998 he also served as vice-Prime minister of Chechnya in Maskhadov's government.

Basayev was considered by some to be the undisputed leader of the radical wing of the Chechen insurgency. He was responsible for numerous guerrilla attacks on security forces in and around Chechnya as well as terrorist attacks on civilians, most notoriously the attack on a school in Beslan, located in North Ossetia, which led to the deaths of more than 385 people, most of them children and the 2002 Moscow theater hostage crisis. ABC News described him as "one of the most-wanted terrorists in the world".