|◄ Preceded by|| Grisha Yeager|
|Followed by ►|
| Frieda Reiss|
| Eren Yeager|
|Mikasa's life, Armin's life, everyone's life, hinges on you being able to control this power!|
|— Grisha to Eren before injecting him with a Titan Serum.|
Dr. Grisha Yeager (グリシャ・イェーガー Gurisha Yēgā?, also spelled as Grisha Jaeger in the FUNimation sub of the anime) was a doctor who lived in Shiganshina District before it fell, and was acknowledged for saving hundreds of lives from a plague that hit the city. He was the father of Eren Yeager, adoptive father of Mikasa Ackerman, and husband of Carla Yeager. He was also a Titan Shifter  and first appeared mysteriously outside the Walls with no memory of his origin, only that he was a doctor.
Dr. Yeager had a gentlemanly appearance. He had straight black hair neatly parted down the middle, a light beard and mustache, and gray eyes. He wore a gray suit with a black vest and a white shirt, a plain bolo tie, and round glasses. In the anime, his hair and eyes are both brown, and he wears a brown suit with a white cravat and a white shirt with ruffled sleeves. He had also been seen wearing a small, black hat with a gray stripe.
As a Titan, he was 15 m tall and had a body with a notoriously bulkier torso than his arms and legs. He had long, dark hair, elongated ears, small eyes, and his mouth was covered in flesh and a dark, thick beard along with black chest hair. His Titan form had several similarities with Eren's, including their long dark hair, elongated ears, sunken eyes, and a muscular physique. His titan form somewhat resembled that of Zeke's, in the fact they both possessed large and wide torsos.
About 20 years before the coronation of Historia, Grisha Yeager was found wandering outside the Walls, near the Shiganshina District, by Keith Shadis. The soldiers were very surprised to see him, not only because he was outside the walls, but also because he suffered amnesia and he had no memories about the civilization inside the Walls and the military. He was taken to a cell by Keith and Hannes, where he says that he remembered his name. After being released, Grisha told Keith that he remembered being a doctor and asked him for knowledge about the world inside the Walls.Keith takes Grisha to a pub in Shiganshina where Keith taught him about the world. Grisha recognizes the work of the Survey Corps, which surprises Keith. There, Grisha also meets Carla, his future wife. Grisha eventually found work at a hospital. He proved to be a talented medic, and his relationship with Carla grew stronger. They finally married, which made Keith very sad, as he too had fallen in love with Carla.
The day Wall Maria fell, Grisha took Eren to the forest after learning of the death of his wife. Keith tried to stop him, but Grisha just told him not to get involved. That is the last time Keith saw Grisha.
Before the fall of Wall Maria, Grisha Yeager was visiting Mr. Ackerman and Mrs. Ackerman to a medical revision. When he arrives there, he finds them dead for hours. He asks Eren if he has seen the girl named Mikasa anywhere, but he is too shocked to answer. He then tells Eren to wait for him at the foot of the mountain while he finds the Military Police.
After the MPs arrive, Grisha hugs Eren and scolds him for the murders he committed when saving Mikasa, asking if he even understood what he had done. However, instead of continuing to scold him for killing Mikasa's kidnappers, he tells him that this time he was lucky and he could have been killed himself. Mikasa, cold and depressed, asks Grisha where her home is and states that she is cold and wants to leave. In response, Eren gives her his scarf and Grisha tells her to come live with them.
StoryMikasa Ackerman. He keeps the basement of his house locked and does not allow anyone inside. Before Wall Maria fell, he promised Eren that he would show him what was in the basement when he got back from a journey.
After the fall of Wall Maria, a tearful Grisha injects a serum into Eren's left arm, which Eren believes is responsible for giving him the ability to shift into a Titan. Telling Eren that the serum will cause him memory loss, Grisha gives him the key to the basement, saying that all of the answers can be found there, and that "their memories" will guide him. What became of Grisha after this moment remained unknown for five years.
After Eren finally succeeds in the use of Vertical Maneuvering Equipment, head instructor of the 104th Training Corps Keith Shadis expresses to himself that Grisha would be proud of his son, Eren, and that he is finally becoming a soldier.
When Eren transforms into a Titan, during experiments conducted by Hange, they ask him to try and communicate with them and the other Survey Corps personnel. He writes on the ground that he does not know how to harden his body. He then sloppily writes, "What my father did to me", referring to Grisha. As he rests after the experiment, Eren wonders where his father is and why he thought of him at that moment.Wall Maria after the Colossus Titan breaches it, Keith Shadis is visible a few steps ahead of Grisha and looking back at him. Then we see Grisha moving toward the chapel that then stood above ground over the cavern, finding his way underground, and pleading with the gathered members of the Reiss family: Rod, his wife, and their five children. He then transformed into his Titan form and killed every Reiss except Rod, who escaped, and Historia, who was not present. During this attack, he battled at least one other Titan, a female, whom he ate. He then destroyed the chapel. Later, in the woods, he gave 10-year-old Eren the key to their basement in Shiganshina. He then injected Eren with a serum that caused him to transform into a Titan. The transformed Eren consumed Grisha, reverted back to his human form, and began to wail in horror at the grisly remains of his father.
Rod later reveals that Grisha confronted the Reiss family in the chapel with a frightened expression on his face. His daughter Frieda Reiss stood in front of her family, protecting them. Grisha then stabbed himself through the hand with a knife and transformed; Frieda shifted by biting her hand. Rod states that Grisha was after Frieda's Titan power, and though it was "invincible," she was not experienced enough to defend herself. Grisha ate her, obtaining that power, and then brutally slaughtered the remaining Reiss family. Among the victims were 14-year-old Dirk and 12-year-old Abel, both of whom Grisha crushed with his hand. He also stomped on 10-year-old Florian and the girl's mother, and squeezed Rod's eldest son Ulklin to death. Finally, he destroyed the chapel. Rod and Historia were the only members left alive, Rod due to fleeing blindly and Historia due to not being present.It is later stated that he stole the power from the Reiss family because each holder of the Coordinate would not only receive the power, but fall under the ideology of the First King, who deemed a world ruled by Titans as a true peace. So long as they were the users of the Coordinate, none of them would ever stop the Titans, even when they have the power to do so and the only hope to use the Coordinate against the Titans was giving the power to a member of another bloodline. Since Eren vowed to kill the Titans for Carla's death and was not under the influence of the Reiss family and therefore the First King, he could accomplish what the family would never do.
After Eren received more memories of his father thanks to Historia, he searched for the man that his father met the day Wall Maria fell. Eren finally realizes that he is Keith Shadis.
Afterwards, in the aftermath of the battle for Shiganshina, War-chief Zeke encounters Eren, noting that the young man looks nothing like his father Grisha. Zeke claims to be a victim of Grisha just like Eren, who he claims was brainwashed by him. As Eren thinks on Zeke's words, he notices an uncanny resemblance between the War-chief and his father.
Grisha was a very skillful doctor, being able to cure hundreds of people from a sickness that attacked mankind. When Carla got sick, he not only could cure her, but also her family. Grisha also was able to find a medicine that could stop said plague.
Grisha Yeager's Statistics :
Grisha was able to turn into a very large Titan; it appeared that he had all of the regular abilities of Titan Shifters, like extraordinary regeneration, incredible strength, and endurance when he is transformed. Other than these, it is unknown if he had any other unique abilities. He had some experience with Titan Shifting; that was the reason why he managed to kill and eat Frieda Reiss, a Titan Shifter that almost matched his size and possessed the Coordinate. He stabbed his own hand with a knife in order to trigger the transformation.
- The Coordinate: After eating Frieda, he possessed this power for a very short amount of time. However, he did not make use of it before passing it on to Eren.
- Regeneration: As a Titan Shifter, it is believed that he could regenerate his body faster than regular humans, even from fatal wounds.
- Eren Yeager - Grisha was perhaps closer to Eren then anyone else in his life, surpassing even his relationship with Carla. As a father, Grisha left home a lot on medical duties, however, he encouraged Eren's dreams to venture outside the wall and offered to reveal to him the secrets of the basement. However, when Wall Maria fell, Grisha took it upon himself to do all he could to stop the Reiss family and then entrusted the very fate of the world to Eren. Grisha spoke of Eren as 'different' when he was questions by Keith, and put an enormous amount of trust into his son. Grisha believed in his son's ability so sincerely that he allowed himself to be devoured, believing that Eren would one day stop the Titans.
- Carla Yeager - Grisha was very taken by Carla, as they married not soon after he had cured her and her family. However, Grisha did not put all his trust in Carla, as he did not share with her his secrets off the outside world. When Grisha heard of Wall Maria's downfall, he shed tears in fear that his family had perished. When Eren and Grisha met after the fall, he was told by his son that the Titan has eaten Carla and, after a moment of silence, told Eren to get revenge for Carla and took him away. Grisha was visibly affected by her death and when turning Eren to a Titan, was told that her death has made him crazy as his son screamed.
- Mikasa Ackerman - Grisha knew Mikasa when she was a small child from visiting her home as the family doctor. When taking Eren along for a visit he had hoped that the two would be able to get along as friends. After her rescue from the human traffickers Grisha showed sympathy toward Mikasa and told her to come live with him and his family. Years later, after the fall of Wall Maria, Grisha mentions her name as he sheds tears in fear that she had been killed by the Titans. Before giving Eren and injection of the Titan Serum, Grisha mentions Mikasa as one of the people Eren must save.
- Keith Shadis - Keith was a special friend to Grisha, as he was the one to bring him inside the walls and nurture him of the society within. Grisha referred to Keith as special and chosen, both of which deeply resonated with Keith. Grisha viewed as a very admirable man, however, as the years went on their relationship declined. Distance grew between them as Keith believed that he was not special or chosen, he had blamed Grisha for leading him to misunderstand himself. Ties with them loosened more so when Grisha married Carla, the woman Keith sought. Before Grisha's death, their relationship appeared to still be stable as Grisha ran toward Keith in a panic, however, they two were on much worse terms as Keith accused Grisha of "cursing another person" to which he responded by saying "this child is not like you".
- Mr. Ackerman & Mrs. Ackerman - Dr. Yeager was well known to the Ackermans as their family physician. They appeared quite friendly when speaking about each otherand Grisha had been known to have been their Doctor at least since Mikasa was small, however it appears that as she grew older his visits were less frequent. Grisha seemed quite disturbed at the sight of his clients' death.
- Zeke - Zeke mentions that he and Eren are "victims" of Grisha. This likely means that Zeke knew Grisha from before he gave up his life for Eren. They could possibly be closely related, as can be seen in their faces bearing a striking resemblance to each other.
- The appearance of Grisha's Titan may be a reference to the giant Surtr of Norse mythology. According to mythology, he is the leader of the fire giants in the south, the ruler of Muspelheim, and, at Ragnarok, his hordes will rush to the north like a southern wind to overwhelm the gods.
- Keith says on the day he found Grisha, there were no Titans in the area, similar to the Beast Titan.
- Grisha was the first human seen in the series who secretly possessed the Titan Shifting ability.