Lashkar-e-Islam, also written as Laskhar-i-Islam, is a Deobandi jihadist terrorist group operating in Khyber District, Khyber-Pakhtunkhwa Province, Pakistan and the neighboring Nangarhar Province, Afghanistan.

Deobandi jihadism is a militant interpretation of Islam that draws upon the teachings of the Deobandi movement, which originated in the Indian subcontinent in the 19th century. The Deobandi movement underwent three waves of armed jihad. The first wave involved the establishment of an Islamic territory centered on Thana Bhawan by the movement's elders during the Indian Rebellion of 1857, before the founding of Darul Uloom Deoband. Imdadullah Muhajir Makki was the Amir al-Mu'minin of this Islamic territory. However, after the British defeated the Deobandi forces in the Battle of Shamli, the territory fell. Following the establishment of Darul Uloom Deoband, Mahmud Hasan Deobandi led the initiation of the second wave. He mobilized an armed resistance against the British through various initiatives, including the formation of the Samratut Tarbiat. When the British uncovered his Silk Letter Movement, they arrested him and held him captive in Malta. After his release, he and his disciples entered into mainstream politics and actively participated in the democratic process. In the late 1979, the Pakistan–Afghan border became the center of the Deobandi jihadist movement's third wave, which was fueled by the Soviet–Afghan War. Under the patronage of President Zia-ul-Haq, its expansion took place through various madrasas such as Darul Uloom Haqqania and Jamia Uloom-ul-Islamia. Jamiat Ulema-e-Islam (S) provided political support for it. Trained militants from the Pakistan–Afghan border participated in the Afghan jihad, and later went on to form various organizations, including the Taliban. The most successful example of Deobandi jihadism is the Taliban, who established Islamic rule in Afghanistan. The head of the Jamiat Ulema-e-Islam (S), Sami-ul-Haq, is referred to as the "father of the Taliban."