Robin is the second oldest member of the crew and an experienced archeologist. She has the powers of the flower flower devil fruit, which allows her to grow replicas of her body parts (arms, legs) at will. She has had a bounty on her head of 79 million berries since she was 8 years old, and when the Straw-hats find her, she's serving under Crocodile, leader of the criminal organization Baroque Works.

After defeating Crocodile at Arabasta, Luffy saves her from a certain death. A little later, she shows up at the Going Merry asking Luffy to take responsability for saving her life when she didn't want him to. She asks to join the crew and he accepts, despite the rest of the crew's initial reluctance. Robin's goal is to find and decypher the poneglyphs, items which are said to hold the key to the World's "100 years void", and the cause of her homeland's, Ohara's, annihilation by the World's Government when she was a child.