This paper will examine the worldview of the late Ottoman ulema regarding the concept of ittihâd-ı İslâm. As highlighted in the works of Ismail Kara, ittihâd-ı İslâm brought together two key concepts in late Ottoman thought: ittihâd – unity in the face of the many divisions and nationalisms that threatened the existence of the empire; and the idea of the transnational Islamic ümmet/millet under the umbrella of the caliphate. A considerable amount of Ottoman political and journalistic writing in the Second Constitutional Period (1908-1920) utilizes ittihâd-ı İslâm as a conceptual paradigm. However, existing secondary literature limits the notion of ittihâd-ı İslâm to the concept of “pan-Islamism”. The latter refers chiefly to: i) Sultan Abdülhamid II’s (r. 1878-1908) foreign policy towards Muslim subjects in largely colonial, non-Ottoman territories, ii) British fears of the unifying impact of such a policy in their colonial domains, particularly India. Due to its association with Hamidian policy, there is little work on the articulation of the thought-world of ittihâd-ı İslâm during the Second Constitutional Period. By surveying primary source literature in Ottoman Turkish and Arabic, chiefly writings of ulema such as şeyhülislam Mustafa Sabri Efendi (d. 1954), Zahid al-Kawthari (d. 1952), and the activist founder of the İttihâd-ı Muhammedî Cemiyeti (The Muhammedan Union), Derviş Vahdeti (d. 1909), the paper will attempt to present the thought-world of late Ottoman thinkers regarding ittihâd-i İslâm outside the restrictive prism of pan-Islamism as foreign policy.