Effendi (a Turkish title meaning a lord or master. is a title of respect, equivalent to the English sir, in Turkey and some other Eastern countries. It follows the personal name, when it is used, and is generally given to members of the learned professions, and to government officials who have no higher rank, such as Bey or Pasha. It may also indicate a definite office, as Hakim effendi, chief physician to the sultan. The possessive form effendim (my master) is used by servants and in formal intercourse.

The 1911 Encyclopædia Britannica claims that it comes corrupted from the Greek authentes (aphentes in Modern Greek] "lord") but this etymology is unlikely.

The term most likely derives from the Old Turkic apandi, a title of nobility. The word also appears in Old Uighur.