John Carter, a modern-day U.S. soldier in Afghanistan, is mysteriously teleported to the planet Barsoom (Mars) via government technology. On Mars, he discovers a world with different gravity, allowing him to leap great distances and exhibit superhuman strength. He meets Dejah Thoris, the beautiful Martian princess, and becomes entangled in a conflict between alien factions.

As Carter helps defend Dejah Thoris and her people, he gradually becomes a hero of Barsoom. The story focuses on his adaptation to the new world, the war between the Martian races, and a budding romance with the princess.