(Turkish: “valley lord”), any of several feudal lords in Anatolia who, from the early 18th century, became virtually independent of the Ottoman central government. After these feudatories disappeared in the 19th century, the term came to designate great hereditary landlords in southern and eastern Turkey who exercised “quasi-feudal” rights over the peasants.

The financial and military obligations of the derebeys to the central government came to be well defined: in time of war they served, with their own men, in the Ottoman armies and were given titles by the sultan, as deputy lieutenant governors and tax collectors. They were, however, independent within their territories, where they struck deep roots and formed local dynasties with strong loyalties. Moreover, not threatened by short tenures, as were appointed governors, they were able to undertake long-term policies concerning the well-being of their people and the development of trade.

The reliance of the Ottoman government on derebey assistance during the 1768–74 Russo-Turkish War increased their influence, and, during the reign of Selim III (ruled 1789–1807), they not only controlled most provinces of Anatolia but also played an important part in Ottoman affairs. During the reign of Sultan Mahmud II (1808–39), however, the power of most derebeys was broken, and their administrative functions were taken over by appointed governors from Istanbul. The process of centralization continued after Mahmud's death (1839), and in 1866 a military expedition subjugated the remaining derebeys in the Çukurova region.