Perico: He is the owner of the bodega. He is never actually seen in the story, but he provides newspapers for Santiago. Santiago likes the papers because they report baseball scores.
Martin: Like Perico, he doesn't actually appear in the story. He's a cafe owner, and in his own way helps provide for Santiago.
Manolin: He is Santiago's apprentice. He is fairly young (most likely a teenager). Manolin's parents no longer want him fishing with Santiago, because Santiago is not catching any fish. Despite his parents' wishes, Manolin still seeks out ways to help Santiago.
Santiago: He is the protagonist of the story. He is a Cuban fisherman that has had quite a run of bad luck recently. He's not catching anything. He's an extremely experienced and knowledgeable fisherman. He's proud of his abilities yet humble as well. His struggle with the marlin is central to the story.