Trafalgar D. Water Law,[17] more commonly known as just Trafalgar Law (トラファルガー・ロー, Torafarugā Rō?) and by his epithet as the "Surgeon of Death", is a pirate from the North Blue and the captain and doctor of the Heart Pirates.[1][6] He is one of twelve pirates who are referred to as the "Worst Generation".[1][18] He became one of the Seven Warlords of the Sea during the timeskip,[2] but his position was revoked for allying with the Straw Hat Pirates.[13] Like many other pirates, Law has dreams of finding the One Piece, while also desiring to know the purpose of the Will of D.[19][20]

Law is the only known survivor of Flevance, a town whose inhabitants suffered from a condition known as Amber Lead Syndrome. Because the disease was fatal and poorly understood, Flevance was destroyed by neighboring countries out of fear (including Law's parents and younger sister), with a young Law barely escaping alive.[7] He subsequently joined the Donquixote Pirates, where Donquixote Doflamingo intended to make Law one of his executive officers.[21] However, thanks to the efforts of Doflamingo's brother, Rosinante, Law was freed from the Donquixote Pirates' influence and became a pirate set to bring down Doflamingo's empire. Before his death, Rosinante fed Law the Ope Ope no Mi, a famed Devil Fruit that allows him to freely rearrange the bodies of others within his domain.

As part of his plan, Law allied himself with Monkey D. Luffy, and together they not only defeated Doflamingo, but also Kaidou and Big Mom, two of the Four Emperors. However, upon leaving Wano Country, he was ambushed by Blackbeard and was defeated in battle; his crewmate Bepo was forced to retreat with Law and leave the rest of their crew, as well as their destroyed submarine, behind.

During the timeskip, his bounty increased from Beli 200,000,000[1] to Beli 440,000,000[2] before it was frozen due to his induction into the Seven Warlords of the Sea. However, after having his title revoked during the events of the Dressrosa Arc, Law's bounty was reinstated and raised to Beli 500,000,000.[13] Eventually, his bounty would be raised to Beli 3,000,000,000 for his role in taking down Big Mom of the Four Emperors alongside Eustass Kid during the Wano Country Arc.[12]

Law joined forces with the Straw Hat Pirates for a brief moment during the Sabaody Archipelago Arc and later on saved Luffy's life at the very end of the Marineford Arc. He is one of the central allies of the Straw Hat Pirates during the Dressrosa, Whole Cake Island, and Wano Country Sagas. He also acts as an ally of the Straw Hats in the movies One Piece: Stampede and One Piece Film: Red.