Background
He was the son of January II of Lannoy (killed in the Battle of Azincourt) and Jeanne de Croÿ, daughter of Jean I de Croÿ, also killed at Azincourt.
He was the son of January II of Lannoy (killed in the Battle of Azincourt) and Jeanne de Croÿ, daughter of Jean I de Croÿ, also killed at Azincourt.
As a young man, January III had a military career, fighting against the Prince-Bishopric of Liège (1430), England (1436), Lorraine (1440) and the Electorate of Cologne (1447). In 1448 he was appointed by Philip the Good as stadtholder of the County of Holland and Zeeland, a function he held until 1462. Between 1459 and 1463, he was also stadtholder of Lilloise Flanders.
In 1452-1453 he participated in the submission of the Revolt of Ghent (1449–1453).
In 1468 he came into conflict with Duke Charles the Bold because of his good contacts with the French Court. He was forced to flee, but later reconciated with Charles.
In 1477 he served Maximilian I of Austria as Chamberlain and conducted several diplomatic missions. He played a very important role in the conclusion of the Treaty of Arras (1482).
He was a member of the noble de Lannoy family.