When new governor Weatherby Swann (Jonathan Pryce) and his 12-year-old daughter, Elizabeth sail to Port Royal, Jamaica, their ship, the HMS Dauntless happen upon a shipwreck and its sole survivor, the young Will Turner. Elizabeth discovers a gold skull medallion around the unconscious Will's neck. Fearing he will be arrested as a pirate, she takes and hides it. She then glimpses a ship with shredded black sails vanishing into the mist.
Eight years later, Captain James Norrington (Jack Davenport) of the British Royal Navy is promoted to Commodore. At his ceremony, he proposes to Elizabeth (Keira Knightley), who faints and tumbles off a wall and into the bay before answering. The skull medallion she is wearing emits a mysterious pulse through the water.
Meanwhile, pirate Captain Jack Sparrow (Johnny Depp) has arrived in Port Royal to steal a ship. While attempting to commandeer the HMS Interceptor, he sees Elizabeth fall into the bay and rescues her. He is promptly arrested for piracy, but escapes and ducks into a blacksmith shop. There he encounters Will Turner (Orlando Bloom), now a blacksmith's apprentice and self-taught expert swordsman. Following a swordfight with Turner, Sparrow is knocked unconscious by the blacksmith and jailed.
That night, Port Royal is besieged by the Black Pearl — a pirate ghost ship. The mysterious pulse from Elizabeth's medallion called to them. The pirates ransack the town seeking the medallion - the last Aztec coin they need to break the curse they're under. Elizabeth is captured and invokes parley—an agreement ensuring one's safety until meeting and negotiating with the opposing side. To protect her identity, Elizabeth tells Captain Hector Barbossa (Geoffrey Rush) that her last name is "Turner". She persuades the pirates to cease the attack on Port Royal in exchange for the medallion, but Barbossa employs a loophole in their negotiation and keeps Elizabeth prisoner.
When he is unable to convince Commodore Norrington to take immediate action to rescue Elizabeth, Will, who is in love with her, seeks assistance from Jack Sparrow. The imprisoned pirate agrees to help if Will frees him from jail, only after he learned his name. After hijacking the HMS Interceptor and recruiting a crew in Tortuga with help from Jack's friend, Gibbs, Jack and Will set sail for Isla de Muerta, a mysterious uncharted island where the pirates have gone to break the curse.
While en route, Will learns the Black Pearl was formerly commanded by Captain Jack Sparrow. When Jack shared the bearings to a hidden chest of Aztec gold coins, First Mate Barbossa instigated a mutiny and marooned Jack on a small island. Jack escaped after three days.
The pirates found and spent the treasure but soon learned it was cursed—leaving them as immortal skeletal beings whose true forms are only revealed in moonlight. The curse can ony be lifted when every coin and a trace of each pirate's blood is returned to the chest. "Bootstrap Bill" Turner opposed the mutiny and sent one coin to his son, William, believing the crew should remain cursed. In retaliation, Barbossa ordered Bootstrap tied to a cannon and thrown overboard only to realize later his blood was needed to break the curse; a Turner kin must now take his place. Believing Elizabeth is Bootstrap's child, Barbossa poises her over the Aztec chest, anoints the last coin with a trace of her blood and drops it into the chest—the curse remains in effect.
Meanwhile, Sparrow and Turner reach the island. Suspecting Sparrow may betray him, Will knocks him out in the cave. He rescues Elizabeth, and they escape to the Interceptor. Jack barters with Barbossa—in exchange for revealing Bootstrap's real child, he wants to captain the Black Pearl. Jack's negotiations come to naught, however, when the Pearl pursues the Interceptor, sinking her and taking the crew captive. Will reveals that he is Bootstrap Bill's true offspring and demands that Elizabeth and the crew be freed. Otherwise, he threatens to shoot himself and fall overboard, lost forever. Barbossa agrees but craftily applies another loophole and strands Elizabeth and Jack on the same island Sparrow was marooned before. Will is taken back to Isla de Muerta for the ritual.
To speed their rescue, Elizabeth burns a cache of abandoned rum to create a signal fire that is spotted by Norrington. She convinces Norrington to rescue Will by impulsively accepting his earlier marriage proposal ("She's safe just like I promised, she's all set to marry Norrington like she promised, and you get to die for her like you promised. So really, we're all men of our words. Except for Elizabeth who is, in fact, a woman.").
Arriving at the island, Norrington sets an ambush outside the cave. Jack goes inside and persuades Barbossa to form an alliance, telling him to delay breaking the curse until after they have taken the Dauntless and killed the crew. Jack then sneaks a coin from the chest, rendering himself immortal. But whatever Jack's intent is, his plan goes awry when Barbossa orders his crew to infiltrate the Dauntless from underwater, avoiding the ambush outside. Jack's true allegiance is revealed when he suddenly attacks and then shoots Barbossa. Jack tosses his bloodied coin to Will who returns the last two medallions to the chest, breaking the curse. No longer immortal, the fatally wounded Barbossa falls dead. Realizing they are no longer cursed, the now-mortal pirates surrender to the navy.
Back in Port Royal, Jack is about to be executed. Believing Jack does not deserve death, Will rescues him. Both are quickly captured, but Elizabeth lends her support and declares her love for Will. Norrington releases her from their engagement, and Will is pardoned; meanwhile, Jack escapes by falling off the wall into the ocean. His crew, who escaped with the Black Pearl, rescue him. Norrington is impressed enough to allow him one day's head start before pursuing him.
