Lambert III was the pretender to the County of Nantes between 851 and his death in 862.

Lambert was the son of Lambert II of Nantes

Lambert II of Nantes

Lambert II was the Count of Nantes and Prefect of the Breton March between 843 and 851. Lambert ruled the county in opposition to Amaury, the puppet count installed by Charles the Bald, King of West Francia. At his death, the county was effectively in Breton control...

, at whose death in 851, the administration of the region fell effectively to the Bretons. His mother was Tetrata of Lombardy, a daughter of the eldest son of Charlemagne

Charlemagne

Charlemagne was King of the Franks from 768 and Emperor of the Romans from 800 to his death in 814. He expanded the Frankish kingdom into an empire that incorporated much of Western and Central Europe. During his reign, he conquered Italy and was crowned by Pope Leo III on 25 December 800...

, Pepin of Italy. Lambert III married Rotrude of Italy, a daughter of Holy Roman Emperor

Holy Roman Emperor

The Holy Roman Emperor is a term used by historians to denote a medieval ruler who, as German King, had also received the title of "Emperor of the Romans" from the Pope...

 Lothair I

Lothair I

Lothair I or Lothar I was the Emperor of the Romans , co-ruling with his father until 840, and the King of Bavaria , Italy and Middle Francia...

. The Emperor was a first cousin of Lambert's mother, as both were grandchildren of Charlemagne.