Usopp (ウソップ Usoppu) is a fictional character from the anime and manga One Piece.

Usopp is the local liar in his village. Usopp's name is probably based on "Isoppu", the Japanese title of the Boy Who Cried Wolf (a famous liar who does the same kind of false alerts as Usopp) story. Considering that "lie" in Japanese is said "uso", the name Usopp could be a portmanteau name between uso and Isopp, both defining a liar.

Usopp calls himself a pirate and takes in three kids, Carrot (Ninjin, meaning "Carrot", in the original Japanese), Onion (Tamanegi, meaning Onion), and Pepper (Piman, meaning Pepper), as his "crew"; he dubs the groups "Usopp's Pirates", or in the English anime, the "Veggie Pirates".

Usopp is the son of Yasopp, a pirate who is part of Red-Haired Shanks' crew. He lies to relieve himself of the pain of having his father not coming back in time to save his mother from dying by illness.

When the Black Cat Pirates came to town, Usopp, along with Monkey D. Luffy, Roronoa Zolo (Roronoa Zoro in Japan), and Nami, fight the pirates and their leader, Captain Kuro. When Kaya shows up on the scene, Kuro, a.k.a. "Klahadore", orders his men to make Kaya write a will that would give him all of her inheritance, before killing her, causing Django to go after Kaya while Luffy, Zoro, Nami, and a critically wounded Usopp to stay behind.

"Usopp's Pirates" run away with Kaya but the group is ambushed by Django in the forest. Django attacks the kids until Kaya threatens to kill herself unless he stopped hurting the kids. Django does this and has her write the will. When Zoro, who was carrying Usopp, approaches, Django prepares to slash Kaya's throat. Usopp's Pirates ram a shovel into him, causing Django to shove the kids away. This gives Usopp enough time to use his secret technique exploding stars on Django, saving Miss Kaya. Django is presumed dead, but he survives and surfaces later on.

After Luffy takes care of the Black Cat Pirates, Usopp disbands "Usopp's Pirates" and leaves them to become the local liars while he joins Luffy, Nami, and Zoro. Usopp becomes a sniper for the crew.

He is voiced by Kappei Yamaguchi in the original Japanese version.