Lieutenant General Georgios Kostidis was born in 1965 in Kastoria. He was admitted to the Hellenic Military Academy (Evelpidon) in 1983 and graduated in 1987 as Armour Second Lieutenant.

He has attended all Armour courses, as well as the Army War College and the Hellenic National Defence College.

During his career, he has served in Armour Units and, as a Commander, he has served in the 289th Medium Tank Company (Samothrace), the 6th Medium Tank Battalion (Vyronia), the 212th Medium Tank Battalion (Lagos), and a ΝΑΤΟ Operational Mentor and Liaison Team (Afghanistan).

He has served as staff officer in ISAF-HQ Operations in Afghanistan, Training and Operations Staff Office Director of the 7th Mechanised Brigade, Operations Staff Officer of the South Eastern Europe Brigade, Training and Exercises Section Chief NRDC-GR, Operational Planning Chair Director in the Supreme Joint War College, Deputy Commander of the 34th Mechanised Brigade, and Director of the Operations Directorate of the Hellenic First Field Army/European Union Operations Headquarters.

In 2017, he was promoted to Brigadier General and assumed Command of an Operational Formation abroad.

In 2019, he was promoted to Major General and assigned as Commanding General of the Service Support Division. In March 2020, he was assigned as Deputy Commanding General of D’ Army Corps.

On 09 March 2021, he was assigned as Commandant of the Hellenic Military Academy (Evelpidon).

On 08 March 2022, he was promoted to Lieutenant General and assigned as Commanding General of the Supreme Hellenic Army Support Command.

On 12 January 2024, upon decision of the Governmental National Security Council, he assumed the duties of Chief of the Hellenic Army General Staff.

Lieutenant General Georgios Kostidis has been awarded all decorations, commendations, and medals provided for his rank.

He holds a Masters Degree in Management of Operational Planning from Nottingham Trent University.

He speaks English fluently.

He is married and has two sons.