Lambert I (died 836) was the
Count of Nantes and
Prefect
Prefect (from the Latin ''praefectus'', substantive adjectival form of ''praeficere'': "put in front", meaning in charge) is a magisterial title of varying definition, but essentially refers to the leader of an administrative area.
A prefect's ...
of the
Breton March between 818 and 831 and
Duke of Spoleto between 834 and 836. Lambert succeeded his father
Guy.
Lambert participated in an expedition undertaken by
Louis the Pious
Louis the Pious (german: Ludwig der Fromme; french: Louis le Pieux; 16 April 778 – 20 June 840), also called the Fair, and the Debonaire, was King of the Franks and co-emperor with his father, Charlemagne, from 813. He was also King of Aqui ...
in 818 against the
Bretons
The Bretons (; br, Bretoned or ''Vretoned,'' ) are a Celtic ethnic group native to Brittany. They trace much of their heritage to groups of Brittonic speakers who emigrated from southwestern Great Britain, particularly Cornwall and Devon, m ...
, who had proclaimed
Morvan Lez-Breizh their king. In 822, a new Breton chief
Wiomarc'h rebelled, but submitted in May 825 at
Aachen. On his return to Brittany, Lambert had him assassinated.
In 831, Lambert joined the rebellion of
Lothair I
Lothair I or Lothar I ( Dutch and Medieval Latin: ''Lotharius''; German: ''Lothar''; French: ''Lothaire''; Italian: ''Lotario'') (795 – 29 September 855) was emperor (817–855, co-ruling with his father until 840), and the governor of Bav ...
against Louis and was exiled across the
Alps
The Alps () ; german: Alpen ; it, Alpi ; rm, Alps ; sl, Alpe . are the highest and most extensive mountain range system that lies entirely in Europe, stretching approximately across seven Alpine countries (from west to east): France, ...
,
[''The Carolingian Kingdoms(840-877)'', Rene Poupardin, ''The Cambridge Medieval History: Germany and the Western Empire'', Vol. 3, Ed. J. B. Bury, (MacMillan Company, 1922), 47.] where he was given the