The cause of death remains unclear and a necropsy is planned.
Lonesome George's caretaker found the tortoise's remains stretched out in the ''direction of his watering hole'' on Santa Cruz Island, in the Galapagos.
Lonesome George was discovered on Pinta Island in 1972 at a time when tortoises of his type were already believed to be extinct. Repeated efforts to breed George failed.
Tortoises were hunted for their meat by sailors and fishermen to the point of extinction, while their habitat has been eaten away by goats introduced from the mainland.
Some 20,000 giant tortoises still live on the Galapagos.
Two females from the Espanola tortoise population (the species most closely related to Pinta tortoises genetically) were with George until the end.