贝伊（土耳其语：Bey；哈萨克语：Би），是突厥语中“首领”或“酋长”之意，后来成为奥斯曼帝国属地以及中亚、南亚地区伊斯兰教人士的一种头衔，有“总督”、“老爷”等意思。

贝伊一词的语源还存有争议。有一种理论是来自中古汉语“伯”字。乌孙的靡也与其有关。当代土耳其语中的“巴依”（Bay）一词，已经失去首领的意思，而只是对成年男性的尊称，可以译作“先生”。

奥斯曼帝国的前几位君主的头衔就是“贝伊”，1383年穆拉德一世被哈里发授予苏丹称号后方停用。此后，贝伊成为次于帕夏的一种称呼。在穆罕默德·阿里统治下的埃及，贝伊成为低于帕夏的一个贵族级别。在突尼斯，贝伊成为君主及其家族的头衔。

Bey (Ottoman Turkish:باي‎/Bey, Arabic:بك‎ / Bek, Persian:بگ‎‎ / Beg or Beyg) is a Turkish title for chieftain, traditionally applied to the leaders (for men) of small tribal groups. The feminine equivalent title was Begum. The regions or provinces where "beys" ruled or which they administered were called beylik, roughly meaning "emirate" or "principality" in the first case, "province" or "governorate" in the second (the equivalent of duchy in other parts of Europe). Today, the word is still used informally as a social title for men (somewhat like the English word "mister" and the French word monsieur, which literally means "my lord"). Unlike "mister" however, it follows the name and is used generally with first names and not with last names.