The Treaty of Kk Kaynarca (Turkish: Kk Kaynarca Antlamas; Russian: - ), formerly often written Kuchuk-Kainarji, was a peace treaty signed on 21 July 1774, in Kk Kaynarca (today Kaynardzha, Bulgaria) between the Russian Empire and the Ottoman Empire, ending the Russo-Turkish War of 176874 with many concessions to Russia. The treaty was a milestone in the history of the decline of the Ottoman Empire, as for the first time a foreign power had a say in the governance of the Porte in assuming direct responsibility for the fate of the Empire's Orthodox Christian subjects.

The Russo-Turkish War of 1768–1774 was a major armed conflict that saw Russian arms largely victorious against the Ottoman Empire. Russia's victory brought Kabardia, part of Moldavia, the Yedisan between the rivers Bug and Dnieper, and Crimea into the Russian sphere of influence. Though a series of victories accrued by the Russian Empire led to substantial territorial conquests, including direct conquest over much of the Pontic–Caspian steppe, less Ottoman territory was directly annexed than might otherwise be expected due to a complex struggle within the European diplomatic system to maintain a balance of power that was acceptable to other European states and avoided direct Russian hegemony over Eastern Europe.Nonetheless, Russia was able to take advantage of the weakened Ottoman Empire, the end of the Seven Years' War, and the withdrawal of France from Polish affairs to assert itself as one of the continent's primary military powers. The war left the Russian Empire in a strengthened position to expand its territory and maintain hegemony over the Polish–Lithuanian Commonwealth, eventually leading to the First Partition of Poland. Turkish losses included diplomatic defeats that saw its decline as a threat to Europe, loss over its exclusive control over the Orthodox millet, and the beginning of European bickering over the Eastern Question that would feature in European diplomacy until the collapse of the Ottoman Empire in the aftermath of World War I.