Usopp, also known as Lysop and later by the titles Sogeking and God Usopp, serves as the sniper of the Straw Hat Pirates. He is the son of Yasopp, a sharpshooter in the Red-Haired Pirates, and the late Banchina. He was born and raised in Syrup Village in the East Blue, where he inherited his distinctive long nose from his mother. After his father left to join Shanks's crew, Usopp spent his childhood caring for his ill mother and trying to lift her spirits by shouting that pirates had arrived, hoping his father would return. Following her death, he continued telling tall tales and alarming the villagers, gaining a reputation as a compulsive liar. He formed a group of local children called the Usopp Pirates and became a close friend of the wealthy, bedridden Kaya, entertaining her with stories.

Usopp is naturally cowardly, anxious, and deeply insecure, often exaggerating his own accomplishments and fleeing from danger. However, he is also highly imaginative, sentimental, and creative, with a strong sense of loyalty to his friends. When his crewmates or innocents are truly threatened, he is capable of putting aside his fear and standing up to overwhelming foes. His core motivation is to become a brave warrior of the sea, just like his father, a goal that drives his personal growth throughout the journey.

His role within the Straw Hat crew is primarily as the sniper, providing long-range support with exceptional accuracy. Before the arrival of a dedicated shipwright, he also acted as the crew's unofficial repairman, maintaining the Going Merry and eventually inventing gadgets such as the Clima-Tact for Nami. He designed the crew's iconic jolly roger. After the two-year timeskip, he serves as a senior officer in the Straw Hat Grand Fleet.

Usopp's key relationships include his deep bond with captain Monkey D. Luffy, who admires Yasopp and respects Usopp as a friend. This bond was severely tested during the Water 7 arc when a disagreement over the irreparable Going Merry led to a fight and Usopp's temporary departure from the crew. He later returned under the masked identity of Sogeking to help rescue Nico Robin at Enies Lobby and formally apologized to rejoin. He shares a brotherly dynamic with Roronoa Zoro, who often scolds him but respects his growth, and a partnership with Nami, as both are more strategically cautious than the stronger fighters. He also formed a close friendship with Chopper, often serving as an older figure and co-comic relief.

Usopp undergoes significant development. His departure from the crew during Water 7 and his subsequent return mark a turning point where he confronts his insecurities and acknowledges his place among the Straw Hats. Over the two-year timeskip, he trains on the Boin Archipelago, gaining muscle, mastering the use of Pop Greens, and dramatically improving his combat abilities. In the Dressrosa arc, he awakens Observation Haki, allowing him to sense auras from extreme distances. His legendary shot from afar to knock out Sugar freed thousands of people from enslavement as toys, earning him the title God Usopp and a greatly increased bounty.

His notable abilities center on marksmanship using various slingshots, starting with the Ginga Pachinko and later advancing to the Kabuto and Kuro Kabuto. He fires custom ammunition called Stars, which include explosives, smoke, and fire. After Skypiea, he incorporated Dial technology into his arsenal. Post-timeskip, his primary ammunition is Pop Greens, seeds that instantly grow into dangerous plants such as Sargasso, Bamboo Javelin, and Impact Wolf. He is also a skilled inventor, having created Nami's Clima-Tact and various upgrades for the crew's equipment. Despite his lack of physical strength, he is highly resourceful and often wins battles through psychological warfare, trickery, and exploiting his opponents' fears, as seen in victories over Perona and Sugar. His bounty currently stands at five hundred million berries.