Monkey D. Luffy, commonly known as "Straw Hat Luffy" or simply "Straw Hat", is the founder and captain of the increasingly infamous and powerful Straw Hat Pirates. He pursues the legendary treasure left behind by the late Gol D. Roger in order to become the Pirate King and achieve a deeper, untold dream—known only to his crew, family, and closest friends. Luffy believes that becoming the Pirate King means having the most freedom in the world.

Born on Dawn Island, Luffy is the son of the Revolutionary leader Monkey D. Dragon and the grandson of the Marine hero Monkey D. Garp, making him a member of the mysterious "Will of D." Most of his childhood was shaped by Garp and the mountain bandit Curly Dadan, under whose care he grew up alongside and swore brotherhood with Portgas D. Ace and Sabo.

Luffy’s greatest inspiration is the pirate "Red-Haired" Shanks, who inadvertently caused him to eat the Devil Fruit that turned his body into rubber. Shanks later sacrificed his arm to save Luffy’s life and entrusted him with his signature straw hat, a symbol of their vow to meet again once Luffy became a great pirate.

As a pirate, Luffy has opposed numerous regional, national, and global powers. He has taken on notorious East Blue pirates, the Marines, the Seven Warlords of the Sea, Cipher Pol, the World Nobles, and even the Four Emperors of the New World. Despite his youth and relatively short time at sea, Luffy has triumphed over many powerful enemies—invading and indirectly causing the destruction of Enies Lobby, escaping the inescapable Impel Down, influencing the events of the Summit War at Marineford, and defeating three Warlords and one Emperor in direct combat.

Luffy also has an extraordinary ability to inspire loyalty and gain allies. He has personally bonded with every member of his crew and earned the admiration of nations, other pirates, the Revolutionary Army, and even some Marines. He is known for his bold actions, unpredictable nature, and strong moral code.

Due to his actions, lineage, and recklessness, Luffy has gained worldwide infamy. He is a primary target of the World Government, Marine Headquarters, and Fleet Admiral Sakazuki. He is recognized as a prominent figure of the Worst Generation, the unofficial leader of the seven-crew Straw Hat Grand Fleet, and—after defeating Kaidou during the Raid on Onigashima—one of the current Four Emperors, with a bounty of 3,000,000,000 berries.

Following the awakening of his Devil Fruit—formerly known as the Gomu Gomu no Mi, now revealed to be the Hito Hito no Mi, Model: Nika—Luffy has been hailed by some as the second coming of Joy Boy and the mythical Sun God Nika.

He is the main protagonist of the One Piece manga and anime series, created by Eiichiro Oda.