The main character of the series who, after witnessing his mother being devoured by a Titan, dedicates his life to their eradication. After graduating fifth in his cadet class, he is swallowed by a bearded Titan during his first mission in Trost. However, he soon reappears as a 15-meter (49 ft) Titan who fights other Titans on equal ground.

Mikasa is Eren's childhood friend who was taken in by his family. Though she was never officially adopted by the Jaeger family, she felt a strong sense of gratitude toward Eren's parents, though she never thought of them as her own. After she was orphaned by slave traders, Eren saved her life and gave her her iconic scarf. A normally quiet and withdrawn girl, she maintains a stoic expression except when it comes to Eren and her friends.

Armin is Eren's childhood friend who joins him in the Scouts to order to make a meaningful difference in the world, and to fulfill his dream of seeing the outside world. After joining the Training Corps with Eren and Mikasa, Armin initially has an inferiority complex, seeing how he falls short of his companions in combat and endurance. He often laments over his perceived cowardliness and dependence on his friends. However, he excels in academics, and his confidence slowly grows when he realizes he can use his brain and strategic abilities to help his friends.

Hange is a bespectacled Survey Corps veteran and the leader of the 4th Squad. A scientist who studies the Titans, Hange shows little fear when interacting with them, and is thus ecstatic when initially meeting Eren. Hange had a strong hatred against Titans until the discovery of Ilse Langnar's notebook provided some new insight into how the Titans may be able to do this. Hange developed an obsessive interest in Titans, and gets uncomfortably intimate with them but that's because they love doing their job. Hange also invents new special weapons for the Scouts to use, such as a barrel that fires multiple grappling hooks to capture Titans alive.

Reiner is a member of the Marleyan military's Warrior Unit and is the holder of the Armored Titan. As the leader of the infiltration unit responsible for Marley's opening offensive against the Walls, he serves as one of the main antagonists for the manga's first thirteen volumes. As a child, Reiner joined Marley's Warrior Unit so he and his Eldian mother could become honorary Marleyans and be reunited with his Marleyan father.

Falco Grice is an Eldian Warrior candidate working for the Marley government. Originally one of the main candidates to inherit the Armored Titan power. Falco is physically not made to be a man of war and does not excel in the battlefield or at asserting himself. Falco has proven to be a very merciful and compassionate person.