Lembitu (Estonian also: Lembit, died 21 September 1217) was an ancient Estonian senior (elder) from Sakala County and military leader in the struggle against conquest of the Estonian lands by the German Livonian Brothers of the Sword at the beginning of the 13th century. He is the only Estonian pre-Crusade ruler, about whom some biographical information is known (he is mentioned only in the Livonian Chronicle of Henry).