A derebey (Turkish: valley lord) was a feudal lord in Anatolia and the Pontic areas of Lazistan and Acara in the 18th century, with considerable independence from the central government of the Ottoman Empire. The derebeys gradually Ottomanized, i.e. became part in the mechanics of the central government, with the re-strengthening of the Ottoman central power in the 19th century. Many members of derebey families left lasting works serving general welfare, while others were also involved in bitter struggles that gave rise to public revolts, such as that of Atçalı Kel Mehmet Efe.