Grand Masters of the Prieure

This list of Grand Masters of the Prieure de Sion is from Henri Lobineau's Dossiers Secrets. This first set of Grand Masters are also the Grand Masters of the Knights Templar, before the Templars failed to prevent the Saracens from recapturing Jerusalem:

1. Hugues de Payen, 1118-1131
2. Robert de Bourgogne, 1131-1150
3. Bernard de Tremblay, 1150-1153
4. Bertrand de Blanchefort, 1153-1170
5. Janfeders Fulcherine, 1170-1171
6. François Othon de St. Amand, 1171-1179
7. Théodore de Glaise, 1179-1184
8. François Gérard de Riderfort, 1184-1188

These are the Grand Masters from the time they split with the Templars in 1188:

1. Jean de Gisors, 1188-1220
2. Marie de Saint-Clair, 1220-1266
3. Guillaume de Gisors, 1266-1307
4. Edouard de Bar, 1307-1336
5. Jeanne de Bar, 1336-1351
6. Blanche d'Evreux, 1366-1398
7. Nicolas Flamel, 1398-1418
8. René d'Anjou, 1418-1480
9. Iolande de Bar, 1480-1483
10. Sandro Filipepi, 1483-1510
11. Leonardo da Vinci, 1510-1519
12. Connétable de Bourbon, 1519-1527
13. Ferdinand de Gonzague, 1527-1575
14. Louis de Nevers, 1575-1595
15. Robert Fludd, 1595-1637
16. Johann Valentin Andrea, 1637-1654
17. Robert Boyle, 1654-1691
18. Isaac Newton, 1691-1727
19. Charles Radclyffe, 1727-1746
20. Charles de Lorraine, 1746-1780
21. Maximilian de Lorraine, 1780-1801
22. Charles Nodier, 1801-1844
23. Victor Hugo, 1844-1885
24. Claude Debussy, 1885-1918
25. Jean Cocteau, 1918-1963
26. Pierre Plantard de Saint-Claire, 1963-1984?

It seems that Pierre Plantard de Saint-Claire abdicated the Grand Mastership in 1984. If a hereditary principle sometimes applies (as seems likely from the above list) for the selection of a new Grand Master, it is likely that Pierre's son, Thomas Plantard de Saint-Claire is Grand Master today.