The use of heritage discourse to produce, legitimize and reinforce nationalist historical narratives, has been a commonplace strategy in statehood projects. However, this often-exclusionary and resolutely top-down political utility of heritage has been increasingly undermined by its relatively recent articulations as a global value regime that promotes equity, inclusivity and diversity at the intersection of environmentalism and human rights. Attesting to this conceptual expansion of heritage has been the use of heritage in diplomacy, resulting in international projects, exchanges and other forms of interactions that strategically co-mingle nationalist agendas with socially constructive concerns. Turkey has been widely studied as an illustration of these various ideological uses of heritage, their manifestations in both its national politics and diplomatic affairs reflecting the historically shifting dominant nationalist narratives in the country. In keeping with the shifting languages and concerns around heritage, however, an increasing scholarly attention has been directed towards the country’s involvement in global heritage regimes under the lead of UNESCO, and its support for international heritage projects as a supplement for its diplomatic relations. However, from the 1980s to the present, there has also been an increasing number of contestations over heritage in the country's international relations. In this regard, most of the academic focus has been directed towards issues of repatriation and archaeological research permit grants in particular. To contribute to the scholarship on heritage contestations within the context of Turkey, this study will identify and analyse the concept of “de-heritagization” as a distinct practice of coercive power in heritage diplomacy. Through the lens of critical heritage studies, it will discuss several recent examples, predominantly contestations over heritage sites of religious importance such as Hagia Sophia, to illustrate this phenomenon, and make a historical comparison with similar controversies from earlier periods.