Johann Gabriel, Marquis du Chasteler de Courcelles (22 January 1763 – 7 May 1825) was a Walloon, born near Mons, Belgium. He entered the military service of Habsburg Austria at an early age and trained as an engineer at the Ingenieurakademie in Vienna. Serving as Chief of Staff to Spleny in the Turkish War from 1788, he won the Ritterkreuz (Knight’s Cross) of the Order of Maria Theresa for outstanding bravery at the Battle of Focsani in action against the Ottoman Turks.