The Order of the Golden Fleece: a Burgundian, Spanish, or Habsburg order?
The order of the Golden Fleece was founded in Bruges by Philip the Good, Duke of Burgundy, in 1430. When the House of Valois-Burgundy became extinct in male line, the Grand Mastership of the order passed to the husband of Mary of Burgundy, Maximilian of Habsburg (later Maximilian I, Holy Roman Emperor), and subsequently was inherited successively by Maximilian's senior agnatic descendants in the House of Habsburg, who, from 1516 to 1700, also happened to be Kings of Spain. When the Crown of Spain passed to the Bourbons, King Philip V claimed the Grand Mastership of the Golden Fleece based on the fact that Charles II of Spain, in his will, had ceded to him all his dynastic rights, which presumably included the Grand Mastership of the order. However, the Holy Roman Emperor, Charles VI, who was then the most senior living agnatic descendant of Maximilian I, claimed that, under the order statutes, the Grand Mastership could not pass to a descendant in maternal line from Maximilian I until all agnatic lines had been extinct. Accordingly, from 1711 onwards, Charles VI started awarding the Austrian Golden Fleece independently of the Spanish order.
Regardless of the validity of Charles VI's claim, when he died without male issue and the Grand Mastership of the Austrian Golden Fleece passed to Francis, Duke of Lorraine, it appears to me that, even invoking the original statutes, the Grand Mastership should have fallen upon the most senior cognatic line descending from Charles V, Holy Roman Emperor, and, excluding the successors to the French throne who did not claim the Golden Fleece, that would be the Spanish Bourbon line descending from King Philip V (Philippe d'Anjou, great-grandson of Philip IV of Spain). In any case, the Bourbon dynastic claim to the order would be stronger at that point than the claim of the House of Habsburg-Lorraine.
A different point of view, however, is to argue that the Grand Mastership of the Order of the Golden Fleece is not tied to a particular dynasty or dynastic inheritance, but rather to the titular Duke of Burgundy. From that perspective, neither house had a strong claim since the Duchy of Burgundy properly was absorbed into the French Crown Lands in the 15th century and was not held since, either by the Kings of Spain or by the Austrian branch of the House of Habsburg. However, following the War of Spanish Succession, the former Burgundian territories in the Low Countries where the Order of the Golden Fleece was founded in 1430 (the previous "Spanish Netherlands") fell under Austrian rule and, as such, the Austrian Habsburgs came into possession of the treasure and the archives of the order, which were kept in Brussels and were later transferred to Vienna, where they are still kept today, following the French occupation of the Low Countries.
The Bourbon Kings of Spain continued to claim the title of Duke of Burgundy up to the proclamation of the Second Republic in 1931 and continued to award the Spanish Golden Fleece in the condition of Ducs de Bourgogne (with letters of appoinment to the order in French), even though, since the reign of Isabella II, the Spanish branch of the order had increasingly taken up the character of a Spanish national order. Following the restoration of the Spanish monarchy in 1975, King Juan Carlos and King Felipe VI dropped that pretense and, taking for example Princess Leonor's letter of appointment to the order, we can see that it is written in Spanish, rather than French, and issued in the name of Felipe VI, Rey de España, rather than the Duke of Burgundy. The Spanish Fleece is also currently awarded by royal decree published in the Official State Gazette (Boletín Oficial del Estado) and countersigned by the Spanish Prime Minister, underscoring its character as a national Spanish order. However, it still differs from the regular civil orders of Spain like the Order of Carlos III or the Order of Isabella the Catholic because the latter are awarded by proposal of a Spanish minister and awards must be pre-approved in a meeting of the Council of Ministers, whereas appointments to the Order of the Golden Fleece are made on personal nomination from the King of Spain only, consulting, however, the cabinet .
The Austrian branch of the order, on the other hand, lost the backing of a sovereign state authority after the Austro-Hungarian Empire fell in 1918 and is awarded today as a truly dynastic order associated with the titular head of the House of Habsburg-Lorraine. To underscore, however, the Habsburg-Lorraine claim to being the legitimate successors to the Burgundian order, traditionalists point out that the Austrian branch has remained faithful to the original statutes, limiting appointments of knights to male Catholic nobility or royalty, while the Spanish branch has admitted Protestant and even non-Christian knights, as well as women and "common" men, with characteristics that are reminiscent of the modern orders of merit.
The Spanish Fleece, however, remains to this day one of the most exclusive orders in Europe (more so even than the Order of the Garter). In fact, excluding the three members of the order who belong to the Spanish Royal Family (King Felipe VI as Grand Master, King Juan Carlos as former Grand Master, and the Princess of Asturias), there are only 14 living knights of the Spanish Golden Fleece, of whom only four are not foreign royals.