Islamic terrorism is a form of religious terrorism carried out by fundamentalist militant Islamists and Islamic extremists with the aim of achieving various political or religious objectives, such as jihad.

Since at least the 1990s, Islamist terrorist incidents have occurred around the world and targeted both Muslims and non-Muslims. Most attacks have been concentrated in Muslim-majority countries, with studies finding 80–90% of terrorist victims to be Muslim. The annual number of fatalities from terrorist attacks grew sharply from 2011 to 2014, when it reached a peak of 33,438, before declining to 13,826 in 2019. From 1979 to April 2024, five Islamic extremist groups—the Taliban, Islamic State, Boko Haram, al-Shabaab, and al-Qaeda—were responsible for more than 80% of all victims of Islamist terrorist attacks. In some of the worst-affected Muslim-majority regions, these terrorists have been met by armed, independent resistance groups. Islamist terrorism has also been roundly condemned by prominent Islamic figures and groups.

Justifications given for attacks on civilians by Islamic extremist groups come from their interpretations of the Quran, the hadith, and Sharia. These killings include retribution by armed jihad for the perceived injustices of unbelievers against Muslims; the belief that many self-proclaimed Muslims have violated Islamic law and are disbelievers (takfir); the perceived necessity of restoring Islam by establishing Sharia as the source of law, including by reestablishing the Caliphate as a pan-Islamic state (e.g., ISIS); the glory and heavenly rewards of martyrdom (istishhad); and the belief in the supremacy of Islam over all other religions. Justification of violence without permitted declarations of takfir (excommunication) has been criticized.

The use of the phrase "Islamic terrorism" is disputed. In Western political speech, it has variously been called "counter-productive", "highly politicized, intellectually contestable" and "damaging to community relations", by those who disapprove of the characterization 'Islamic'. It has been argued that "Islamic terrorism" is a misnomer for what should be called "Islamist terrorism".

George W. Bush and Tony Blair (US president and UK Prime Minister respectively at the time of the September 11 attacks) repeatedly stated that the war against terrorism has nothing to do with Islam. Others inside and out of the Islamic world who oppose its use on the grounds there is no connection between Islam and terrorism include Imran Khan, the prime minister of Pakistan, and academic Bruce Lawrence. Former US president Barack Obama explained why he used the term "terrorism" rather than "Islamic terrorism" in a 2016 town hall meeting saying, "There is no doubt, ... terrorist organizations like Al-Qaeda or ISIL – They have perverted and distorted and tried to claim the mantle of Islam for an excuse for basically barbarism and death ... But what I have been careful about when I describe these issues is to make sure that we do not lump these murderers into the billion Muslims that exist around the world ..."

It has been argued that "Islamic terrorism" is a misnomer for what should be called "Islamist terrorism".

In January 2008, the US Department of Homeland Security Office for Civil Rights and Civil Liberties issued a report titled Terminology to Define the Terrorists: Recommendations from American Muslims, which opened with

Words matter. The terminology that senior government officials use must accurately identify the nature of the challenges that face our generation. [...] At the same time, the terminology should also be strategic – it should avoid helping the terrorists by inflating the religious bases and glamorous appeal of their ideology.