Lambert III (c. 830–882) was pretender to the County of Nantes.
After his father's death, Lambert III became a pretender to the County of Nantes.
His mother was Tetrata of Lombardy, a daughter of Pepin of Italy, eldest son of Charlemagne.
Lambert III married Rotrude of Italy, a daughter of Holy Roman Emperor Lothair I.
[1] The Emperor was a first cousin of Lambert's mother, as both were grandchildren of Charlemagne.