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.