|Even if the entire world ends up hating you...just know that your dad is always on your side.... So promise me...that you'll come back....|
|— Leonhart to his daughter, Annie|
Leonhart (レオンハート Reonhāto?) is the father and trainer of Annie Leonhart. He relentlessly trained Annie to fight, using mostly kicks and the attacker's weight against them. Memories of his pleas for forgiveness later create an opening for Annie to crystallize herself before Eren Jaeger has the chance to capture her.
Leonhart has a receding hairline with his black hair combed back. He appears to be a relatively short man, as his daughter is also very short, and well built for fighting as he is a trainer. He has only been seen wearing a light jacket over a white shirt with dark pants and shoes.
He seems to be a relentlessly strict trainer, not allowing his daughter to take breaks and yelling at her during the training sessions. However, sometime before Annie's departure, he has a change of heart and apologizes to her, asking her to promise him that she comes back someday, assuring her that he would always be on her side.
Many years ago, Leonhart was relocated to the Liberio internment zone from another country after it was discovered he had Eldian blood. While living in the city, he came across a baby girl who was abandoned for similar reasons; Leonhart decided to adopt the girl and gave her the name Annie. As Leonhart began raising Annie over the following years, he decided to have her become a Warrior so that he could improve his own life. Leonhart taught Annie fighting techniques that involved kicks and the use of the opponent's weight against themselves. Because of his harsh treatment, Annie eventually lashed out at him during training, crippling him for the rest of his life.
Before Annie left their hometown, Leonhart apologized to her, saying that it was too late to ask for forgiveness. However, Leonhart assured her that even if the whole world hated her and treated her like an enemy, he would always be by her side. He asked her only to promise him that she will return home.
During her investigation of the disappearance of Carly Stratmann, Annie is reminded of her relationship with her father after seeing the relationship between Carly and her father Elliot G. Stratmann.
Leonhart attends Willy Tybur's production at the Liberio festival, being seated in reserved seats meant for honorary Marleyans. He speaks with Karina Braun about Bertholdt Hoover's father having passed away, and Mrs. Braun discusses the pride of both Annie and Bertholdt having devoted their lives for Marley. Leonhart denies this, adamantly stating that Annie is not dead, as she promised to come home.
Leonhart listens apathetically whilst Willy delivers his speech, seemingly caring little for his revelations on the true history of the Great Titan War, or his reasons to wage war on Paradis Island. After Willy officially declares war, the Attack Titan comes forth, killing Willy and sending building wreckage into the crowd.
Along with all other Subjects of Ymir, Leonhart is spoken to by Eren Jaeger through the Founding Titan. Leonhart drops his shopping and falls to his knees, panicking about the declaration that the lives beyond Paradis Island will be exterminated.
Leonhart is among a group of Eldians who desperately try to convince Liberio's guards to allow them to leave before Eren arrives with the Wall Titans. Unfortunately, the guards do not believe the crowd, as only Eldians were able to see Eren's broadcast, and accuse the Eldians of plotting to escape their internment camps. The guards begin to detain the group and Leonhart, recalling Annie's promise to return to him, begins lashing out at them.
- Annie Leonhart - At first he seemed to be a strict and not very approachable father for Annie, though for some reason he later changed his mind and demonstrated his love for his daughter by tearfully hugging her and assuring her that he would always be on her side. This reaction seemed to deeply surprise Annie, indicating that it was not common in him until then.
- The name Leonhart is derived from the Spanish word león and the Dutch word hart. These words combined literally translate to Lionheart. Lionheart is a nickname that is given to someone who is a great warrior, which is something that he strives his daughter Annie to be.
- While Leonhart was portrayed with dark blond hair in the first season of the Attack on Titan anime, his hair color was darkened considerably for his appearance in the Wall Sina, Goodbye OVA adaptations.
- Leonhart and Gerald share the same English voice actor.