Xehanort is the main antagonist of the Xehanort Saga, although he has appeared in a diversity of shapes and forms:
- Xehanort, a Keyblade Master, and the catalyst of most of the events in the series so far, effectively making him the true villain of the Xehanort Saga.
- The true Organization XIII, which is composed completely of vessels to carry a fragment of Master Xehanort's heart, as well as every split or fused form of Xehanort.
- Terra-Xehanort, the result of Master Xehanort forcing his heart into Terra's body. He is also known as "Xehanort" and "Ansem", while he is an apprentice to Ansem the Wise.
- Ansem, Seeker of Darkness is the Heartless of Terra-Xehanort, made from Master Xehanort's heart. He keeps the name Terra-Xehanort stole from Ansem the Wise, but he is later referred to only as Xehanort's Heartless.
- Riku-Ansem is an alternate form of Riku that forces him to assume "Ansem"'s form, but also grants him the antagonist's powers.
- Xemnas is the Nobody of Terra-Xehanort, effectively Terra's body stained by Master Xehanort. He founds the original Organization XIII and is initially referred to as "Xehanort".
- Ansem, Seeker of Darkness is the Heartless of Terra-Xehanort, made from Master Xehanort's heart. He keeps the name Terra-Xehanort stole from Ansem the Wise, but he is later referred to only as Xehanort's Heartless.
- Braig was a mercenary hired by Master Xehanort to fight Terra, prior to his battle wih Aqua he becomes host for a piece of Xehanort's heart.
- Xigbar is the Nobody of Braig and a founding member of the original Organization XIII. He has given up his own existence to become a vessel for Master Xehanort as Braig, and now considers himself as already "half-Xehanort."
- Saïx is the Nobody of Isa and the original Organization XIII's second-in-command. Like Xigbar, he gives up his own existence to become a vessel for Master Xehanort.
- Anti-Saïx is a non-canon copy of Saïx encountered in the 358/2 Days mission mode.
- No Heart is a data simulation of Master Xehanort in his Keyblade Armor, and is fought within the "Foresight unto Darkness" battle in the Mirage Arena.