Commandeur is a title in French and Dutch (also, now a purism, Kommandeur), usually rendered in English as Commander, with different uses. The literal meaning is he who commands, parallel to Commandant. In most senses the German equivalent is Kommandeur.
Various functions of commanding officers were styled Commandeur. In the navy of the Dutch Republic anyone who commanded a ship or a fleet without having an appropriate rank to do so, could be called a commandeur. This included ad hoc fleet commanders and acting captains (luitenant-commandeur). In the fleet of the Admiralty of Zealand however, commandeur was a formal rank, the equivalent of Schout-bij-nacht (Rear-Admiral) in the other Dutch admiralties. The Dutch use of the title as a rank lives on in the Royal Netherlands Navy, as the equivalent of Commodore. In the Royal Netherlands Air Force, however, this rank is known by the English spelling of Commodore which is the Dutch equivalent of the British Air Commodore.
Similar rank also exist in the Royal Danish Navy and the Royal Norwegian Navy (as Kommandør), as well as the Swedish Navy (as Kommendör). Note that these are equivalent to Captain in the British Royal Navy and the United States Navy, and not Commodore.
In many orders of knighthood, Commandeur is a high rank, usually above Officier (i.e. Officer), but under one or more ranks with a prefix meaning "Great", e.g. Groot- in Dutch, Grand - in French, which may include Grootcommandeur (Grand Commander; equivalent to Knight), the equivalent of Commendador-mayor (using an equivalent suffix) in Spanish.
- In military orders with extensive territorial possessions, individual estates could be called commenda and enthrusted to an individual Knight, as a de facto fief. Apart from cases where such a fief was ex officio linked to a higher office within the order, his style would then be Commandeur; this etymology is best preserved in the Spanish form Commendador, important in the military orders involved in the Reconquista such as the Order of Santiago.
In this sense only, the equivalent German title is Komthur, of importance mainly in the State of the Teutonic Order and other orders' possessions (throughout Europe).
Colonial office 
As in various small colonial settlements (such as various Caribbean islands) commanding the garrison was the crux of the top job, the military title Commandeur could also be used instead of a civilian gubernatorial style, not unlike the Portuguese Captain-major.
For example, this was the case on the island of Tobago in the Dutch colony of Nieuw Walcheren ('New Walcheren')