Lembitu (year of birth unknown; died on September 21, 1217) was one of the best-known Estonian leaders in the fight against the conquest of German Sword Brethren in the beginning of the 13th century.

Lembitu, also referred to in Estonian as Lembit and in Latin as Lambite, Lembito or Lembitus, was first mentioned in chronicles in the year 1211 with regard to a military expedition. In 1211, troops led by Lembitu destroyed a troop of missionaries in the historical Estonian region of Sakala and made a raid to the Russian town of Pskov. In 1215, Lembitu's Lehola stronghold (situated near the present town of Suure-Jaani) was taken by Germans and Lembitu was captured as a prisoner. He was released in 1217.

Lembitu attempted the unification of all Estonians to stand against the German conquest. He managed to assemble an army of 6000 Estonian men from different counties but was killed in the following Battle of St. Matthew's Day in September, 1217.