- "Only my father calls me Number One."
- —Luther Hargreeves[src]
Luther Hargreeves is one of the forty-three children who were all born on the same day in 1989 to a mother without any previous signs of pregnancy. The baby was one of seven adopted by Sir Reginald Hargreeves with the intention of training them to save the world. Ranked by their individual usefulness, Luther was Hargreeves' Number One and the leader of The Umbrella Academy. He possesses super strength and durability.
Luther was the only member of the Academy who did not leave, and continued to serve Sir Reginald. Sent on a mission to stop a biochemical threat, Luther is critically injured and Sir Reginald is forced to use a serum to save his life. The serum gives Luther an ape-like physiology, greatly increasing his muscle mass and strength. In an effort to give him focus, Sir Reginald sends him to the moon to watch out for threats, and Luther send regular reports back to his father.
Following Sir Reginald's death, Luther comes to believe he was murdered. As events unfold, Luther finds out that Sir Reginald never read any of the reports he sent back and believes that he was sent away for not being a good enough Number One.
As the rest of the Umbrella Academy members "number one" was born on October 1st 1989, somehow he ended up in Sir Reginald Hargreeves' hands, where was raised by him and Grace- who he called dad and mom.
Luther is a loving, protective and righteous individual. He is shown to immediately throw himself in harm's way and act as a shield in dangerous situations and is shown to have a firm belief in right and wrong. He was the only of his siblings to stay at the academy and continue his work as a superhero, trusting his father's commands implicitly. Luther is shown to define himself as the leader of the umbrella academy and as his father's "number 1" taking his role very seriously and devoting his life to his father's cause. As a result, he never left the umbrella academy or developed a life outside of it, becoming isolated and sheltered. He notable mentions that he never even had friends due to his devotion. As a result, he has a somewhat naive, almost childlike aspect to him. When he discovers his father has never read his reports from the moon he is devastated and lost, feeling he wasted his life and causing him to spiral out of control and lash out by going to a rave, taking drugs and getting drunk.
- Super strength: Luther possesses immense strength which is enhanced by his ape-like physiology. As a child, he could easily lift and throw a fully grown adult across a room and through a window.
- Enhanced durability: Luther possesses an extremely durable body due to his ape-like physiology. He is able to shrug off most physical impacts during combat, and could even take the full weight of a falling chandelier without injury. Luther is not invulnerable, however, as Diego managed to cut him with a knife and draw blood, and he is shown to hide from bullets.