Pan-Islamism (Arabic: الوحدة الإسلامية, romanized: al-Waḥdat al-Islāmiyya) is a political movement which advocates the unity of Muslims under one Islamic state, often a caliphate or an international organization with Islamic principles. Historically, after Ottomanism, which aimed at the unity of all Ottoman citizens, Pan-Islamism was promoted in the Ottoman Empire during the last quarter of the 19th century by Sultan Abdul Hamid II for the purpose of preventing secession movements of the Muslim peoples in the empire.
Pan-Islamism differentiates itself from pan-nationalistic ideologies, for example Pan-Arabism, by focusing on religion and not ethnicity and race. It sees the ummah (Muslim community) as the focus of allegiance and mobilization, including the Tawhid belief by the guidance of Quran and Sunnah's teachings.