Synthetic Men of Mars is a science fantasy novel by American writer Edgar Rice Burroughs, the ninth of his Barsoom series.

[1] Like several previous novels in the Barsoom series, Synthetic Men introduces a completely new character as its protagonist: Vor Daj, a padwar (warrior) from Helium and a member of John Carter's personal guard.

Since the events of Master Mind he has transferred his base to a hidden location, which is ultimately found to be the dead city of Morbus in the Toonolian Marshes.

Vor Daj's brain is transplanted into the body of a hormad named Tor-dur-bar to enable him to spy on their captors, and his adventures form the bulk of the story.

Vor Daj is recovered and Morbus, which has been overrun by a huge mass of cancerously growing hormad flesh, is destroyed with incendiary bombs.