The ideas and practices of the leaders, preachers, and movements of the Islamic revival movement known as Islamism (also referred to as Political Islam) have been criticized by non-Muslims and Muslims (often Islamic modernists and liberals).

Among those authors, scholars and leaders who have criticized Islamism, or some element of it, are Maajid Nawaz, Reza Aslan, Abdelwahab Meddeb, Muhammad Sa'id al-'Ashmawi, Khaled Abu al-Fadl, Gilles Kepel, Matthias Küntzel, Joseph E. B. Lumbard, Olivier Roy, and Indonesian Islamic group Nahdlatul Ulama.

Tenets of the Islamist movement that have come under criticism include: restrictions on freedom of expression to prevent apostasy from and insults to Islam; that Islam is not only a religion but a governing system; that historical Sharia, or Islamic law, is one, universal system of law, accessible to humanity, and necessary to enforcement for Islam to be truly practiced.

Explaining the development of Islamism (or at least jihadist Islamism), one critic (Khaled Abou El Fadl) describes it as not so much an expression of religious revival and resurgence, but a phenomenon created by several factors:

According to Graham Fuller, a long-time observer of Middle Eastern politics and supporter of allowing Islamists to participate in politics, "One of the most egregious and damaging roles" played by some Islamists has been in "ruthlessly" attacking and instituting legal proceedings "against any writings on Islam they disagree with."

Some of the early victims of Islamist enforcement of orthodoxy include Ahmad Kasravi, a former cleric and important intellectual figure of 1940s Iran who was assassinated in 1946 by the Fadayan-e Islam, an Islamic militant group, on the charge of takfir.

Mahmoud Mohamed Taha, a 76-year-old "practicing Muslim" and theologian was hanged in a public ceremony in Khartoum, January 18, 1985, for among other charges "heresy" and "opposing application of Islamic law". Taha had opposed Sharia law in its historical form, as it was instituted in Sudan, because he believed the Quranic verses on which it was primarily based (known as the Medina verses) were adapted for a specific place and purpose – namely ruling the seventh-century Islamic city-state of Medina – and were abrogated by verses revealed in Mecca, which (Taha believed) represented the Islamic "ideal religion".

Maybe the most famous alleged apostate in the Arab world attacked by Islamists was Egyptian author and Nobel Prize winner Naguib Mahfouz, who was harassed and stabbed in the neck by assailants, almost killed and crippled for the rest of his life. Others include novelist Egyptian Salahaddin Muhsin who