Lambert Guideschi II Count Nantes was born to Lambert Guideschi Duke Spoleto and Itta Unknown Duchess Spoleto.
In 836 [his father] Lambert Guideschi Duke Spoleto died.
On 25 Jun 841 Lambert Guideschi II Count Nantes fought at Fontenay, Yonne during the Battle of Fontenay: Franks.
On 24 May 843 the Battle of Blain aka Messac was a battle between Brittany and the County of Nantes over control of Nantes which, at that time, was controlled by the Frankish Kingdom. The Franks were defeated.
Lambert Guideschi II Count Nantes commanded the Breton army.
Renaud Count of Herbauges, Poitiers and Nantes, who commanded the army of Nantes, was killed the following day.
In 852 Lambert Guideschi II Count Nantes was killed by Gauzbert Rorgonide I Count Maine.