General Thierry Marchand was born on 27 January 1964 in Bergerac. He is married and has three children. 

After graduating from the École Spéciale Militaire de Saint Cyr in 1987, he joined the Infantry and the Foreign Legion for the first part of his career, which was marked by numerous operational engagements (Gulf War, former Yugoslavia, Somalia, Central African Republic, Chad, etc.).

In 2000, he joined the École de Guerre in Paris as part of the 8th session of the CID. He continued his career as a senior officer in a ministerial cabinet (Michelle Alliot Marie's military cabinet between 2003 and 2006) and then took command of his regiment (2006-2008), the 13th Half Brigade of the Foreign Legion, stationed in Djibouti.

He then joined the Centre for Advanced Military Studies, where he attended the 61st session of the IHEDN in Paris. He then served in the central administration of the Ministry of Defence before joining Jean Yves le Drian's military cabinet between 2012 and 2014.

Appointed general in 2014, he commanded the French Forces in New Caledonia between 2017 and 2019 before taking up the position of Director of Security and Defence Cooperation (DCSD) within the Ministry for Europe and Foreign Affairs. 

He left the military in 2022 and was appointed by the President of the Republic as French Ambassador to Cameroon (2022–2025). 

Currently a Lieutenant General in the second section, he is a Commander of the Legion of Honour and the National Order of Merit.