Morgan, also known by the epithet Axe-Hand Morgan, is a former Marine captain who appears as an antagonist in the early events of the story. Before his introduction, he was a chief petty officer who survived an assault by the pirate Kuro, an encounter that left him with a broken jaw and the loss of his right arm, which was replaced with a massive steel axe. This traumatic event was manipulated by Kuro as part of a plan to fake his own death, and Morgan was hypnotized into believing he had captured the pirate captain. This fabricated success brought him fame and an undeserved promotion, setting him on the path to becoming a corrupted and power-obsessed officer.

As the commanding officer of the Marine base on Shells Town, Morgan rules through pure terror. He is a cruel and tyrannical figure who abuses his authority without restraint, imposing heavy taxes on the citizens and punishing any disobedience, even from his own subordinates, with death. His personality is defined by an absolute obsession with rank and status; he genuinely believes that his position makes everything he does inherently right, and he demands total, unquestioning obedience. This obsession is shown in his refusal to accept defeat, even when completely outmatched. He displays no genuine fatherly affection for his spoiled son, Helmeppo, whom he considers a worthless disappointment. Prior to his fraudulent promotion, Morgan was said to be a brave man who was not afraid of death, suggesting that his present cruelty is a result of power corrupting him.

In his role in the story, Morgan serves as the first significant Marine obstacle that Monkey D. Luffy encounters. His tyranny directly leads to Luffy’s decision to help the aspiring Marine Koby and to free the imprisoned pirate hunter Roronoa Zoro. The conflict begins when Luffy accidentally breaks a newly built statue of Morgan, prompting the captain to confront him. Despite his intimidating presence and the power of his axe-arm, Morgan is unable to land a single blow on the rubber-bodied Luffy and is swiftly defeated. The final blow is delivered by Zoro, who had promised to defeat the captain for him. Morgan's key relationships are largely antagonistic. He is the father of Helmeppo, who initially exploits his father’s name for his own petty cruelties. However, after Morgan’s downfall, Helmeppo disowns him. Morgan also has a significant, unwitting connection to the pirate Kuro, the man responsible for his injuries and his fraudulent rise to power.

After his defeat, Morgan is stripped of his rank and taken away as a prisoner aboard a Marine ship commanded by Vice Admiral Garp. He manages to escape by using his own son as a hostage, slashing the sleeping Garp in the process, and is last seen drifting alone on the ocean. In terms of notable abilities, Morgan possesses considerable physical strength and endurance, being the only survivor of Kuro's attack. His primary weapon is the large axe that replaces his right hand, which he can swing with enough force to create a shockwave capable of slashing through a fence and splitting the ground. He is also knowledgeable about Devil Fruits, recognizing Luffy's rubber body for what it is despite their rarity in the East Blue.