In diplomatic history, the Eastern question was the issue of the political and economic instability in the Ottoman Empire from the late 18th to early 20th centuries and the subsequent strategic competition and political considerations of the European great powers in light of this. Characterized as the "sick man of Europe", the relative weakening of the empire's military strength in the second half of the eighteenth century threatened to undermine the fragile balance of power system largely shaped by the Concert of Europe. The Eastern question encompassed myriad interrelated elements: Ottoman military defeats, Ottoman institutional insolvency, the ongoing Ottoman political and economic modernization programme, the rise of ethno-religious nationalism in its provinces, and Great Power rivalries.

While there is no specific date on which the Eastern question began, the Russo-Turkish War (1828–29) brought the issue to the attention of the European powers, Russia and Britain in particular. As the dissolution of the Ottoman Empire was believed to be imminent, the European powers engaged in a power struggle to safeguard their military, strategic and commercial interests in the Ottoman domains. Imperial Russia stood to benefit from the decline of the Ottoman Empire; on the other hand, Austria-Hungary and Great Britain deemed the preservation of the Empire to be in their best interests. The Eastern question was put to rest after the First World War, one of the outcomes of which was the collapse and division of the Ottoman holdings.