Brook is a fictional character from the manga and anime series One Piece. He is the musician of the Straw Hat Pirates and is recognizable by his appearance as a living skeleton with an afro. He is a Devil Fruit user who ate the Yomi Yomi no Mi, also known as the Revive-Revive Fruit, which allows him to return to life after dying once. Because he found his body long after his death, it had decayed to nothing but bones, leaving him in his current skeletal state.

Before becoming a member of the Straw Hat crew, Brook was the leader of a battle convoy for an unnamed kingdom before joining the Rumbar Pirates as their swordsman and musician. He eventually became the captain of the Rumbar Pirates after their original captain, Yorki, left the crew due to an incurable disease. Around fifty-two years before the main story, Brook and his crew made a promise to a young island whale named Laboon that they would return to him after circumnavigating the world. However, the Rumbar Pirates were later attacked in the Florian Triangle, and their enemies used poison that led to the entire crew's death. As the last surviving member, Brook played a final recording of the crew singing their favorite song, Binks' Sake, on a Tone Dial before he too succumbed to the poison. His Devil Fruit power activated upon his death, but his soul spent a year lost in the fog before finding his skeletal body. For the next fifty years, Brook drifted alone on his ship until he encountered the Straw Hat Pirates.

Brook's personality is eccentric and defined by several notable quirks. He frequently cracks jokes about his skeletal condition, which he calls "skull jokes," and his unique laugh is "Yohohoho". He often asks women if he can see their underwear, a running gag that persists throughout the series. Despite his often humorous demeanor, Brook is also a deeply loyal and grateful individual who greatly values companionship after his decades of isolation. He can be easily frightened by things he considers unnatural, such as ghosts or zombies, which is ironic given his own undead state. Underneath his lighthearted exterior, he carries the sadness of losing his former crew and holds his promise to Laboon as his primary driving motivation. His character demonstrates resilience and an appreciation for life and friendship, despite technically being dead.

As the crew's musician, Brook's role is to provide music for his companions, something the captain, Monkey D. Luffy, had wanted for his crew since the beginning of his journey. He is also a skilled swordsman who fights using a cane sword, employing a fencing-based style. In the story, he joined the Straw Hat Pirates after they helped him recover his shadow, which had been stolen by the Warlord of the Sea, Gecko Moria. He develops key relationships within the crew, often acting as a grandfatherly figure, which the series' author has said represents his role in the Straw Hat family. He forms a bond with the swordsman Roronoa Zoro, who shares his expertise as a fellow fighter, and with Luffy, who appreciates his unique spirit and musical talent.

Throughout the series, Brook experiences significant development. Initially defined by his loneliness and a desire to fulfill his old promise, he gradually becomes a more integrated and vital member of the Straw Hat crew, forming new bonds that give him a renewed sense of purpose. He also gains greater mastery over his Devil Fruit powers. After the two-year timeskip, Brook has learned to harness the true power of the Yomi Yomi no Mi, allowing him to project his soul out of his body for reconnaissance and, most notably, to channel the chill of the underworld through his sword. This ability, which he uses in techniques like those named after musical terms, allows him to freeze his opponents and their weapons.

Brook possesses several notable abilities beyond his swordsmanship. As a skeleton, his body is extremely light, granting him incredible speed and the ability to run across water. He does not have lungs, so he never runs out of breath, and he lacks many vital organs, making him immune to certain types of attacks. He can also detach his limbs and reattach them without issue. His love for music is not just a hobby but a tool in battle; he can play his violin or guitar to create hypnotic or even soul-affecting effects on his listeners. The song Binks' Sake remains deeply significant to him, and he carries the Tone Dial recording of his original crew's final performance inside his skull, preserving their memory.