The Gülen or Hizmet movement is an Islamist fraternal movement. It is a sub-sect of Sunni Islam based on a Nursian theological perspective as reflected in Gülen's religious discourse (oration). It is referred to by its members as the "service" or "community", in which originated from Turkey around late 1950s and institutionalized in 180 countries in that addition to educational institutions owns media, finance, for-profit health clinics, and affiliated foundations that reached a net worth in the range of $20-to-$50 billion in 2015. Both the movement and its organizations led by the Islamic preacher Hoca Fethullah Gülen, who left Turkey under the cloud of the lawsuits and settled in Saylorsburg, Pennsylvania in 1999. The members of the organization who were directly involved at 2016 Turkish coup d'état attempt were put in prison and the members who worked for Turkey’s governmental agencies were dismissed. The movement is designated as a terrorist organization by Turkey, Pakistan, Northern Cyprus, and the Gulf Cooperation Council.

Islamic schools and branches have different understandings of Islam. There are many different sects or denominations, schools of Islamic jurisprudence, and schools of Islamic theology, or ʿaqīdah (creed). Within Islamic groups themselves there may be differences, such as different orders (tariqa) within Sufism, and within Sunnī Islam different schools of theology and jurisprudence. Groups in Islam may be numerous, or relatively small in size.