Một mảnh, Marineford

The fourteenth season of the One Piece anime series was produced by Toei Animation, and directed by Hiroaki Miyamoto. The season began broadcasting in Japan on Fuji Television on June 27, 2010, and ended on September 25, 2011. The season focuses on Monkey D. Luffy as he, Impel Down's escaped prisoners and Whitebeard's pirates goes to the Marineford to save his adoptive older brother Portgas D. Ace from the execution. It contains two story arcs. The first is titled "Marineford" (マリンフォード, Marinfōdo), which mainly adapts the 56th to 59th volumes of the material from the One Piece manga by Eiichiro Oda. The second story arc, which is also titled "Post-War" (戦後, Sengo), also adapts material from the 59th to 61st volumes of the manga.

The season deals with the war between the Marines and Whitebeard's pirates. Focusing on Luffy, Jimbei, and the escaped convicts from Impel Down as they infiltrate Marineford with the help of Whitebeard's pirates to save Ace from the execution. Eventually, Luffy must decide on whether to continue training in two years or go back to Sabaody to see his friends once again. The first DVD compilation was released on October 5, 2011.

The season used three pieces of theme music. The first opening theme, titled "Kaze o Sagashite" (風をさがして; lit. 'Search for the Wind') and performed by Mari Yaguchi with the Straw Hats, continues to be used for the first two episodes. The second opening theme, from episodes 459 to 492, is "One Day" performed by The Rootless. The third opening theme, from episodes 493 to 516, is "Fight Together" performed by Namie Amuro.