Pirates of the Caribbean: On Stranger Tides is a 2011 American adventure fantasy film and the fourth installment in the Pirates of the Caribbean series. In the film, Captain Jack Sparrow (Johnny Depp) is joined by Angelica (Penelope Cruz) in his search for the Fountain of Youth, confronting the infamous, real-life, legendary pirate Blackbeard (Ian McShane). The plot draws inspiration from the novel On Stranger Tides by Tim Powers, which also inspired the LucasArts game The Secret of Monkey Island. It is directed by Rob Marshall, written by Ted Elliott and Terry Rossio, and produced by Jerry Bruckheimer.

The movie was distributed by Walt Disney Pictures and was released in the United Kingdom and Italy on May 18, 2011, in Australia on May 19, 2011, and in the United States and Canada on May 20, 2011.The release was presented in Disney Digital 3-D and IMAX 3D, as well as in traditional two-dimensional and IMAX formats. The film was first announced in 2008 and principal photography started in June 2010. The release was the first in the series to be directed by Rob Marshall and not Gore Verbinski. It was also the first movie in the series which featured fictional versions of historical characters such as Blackbeard, George II of Great Britain, Henry Pelham, John Carteret and Ferdinand VI of Spain. It was the first Pirates of the Caribbean film to be released in 3D and Jerry Bruckheimer's second 3D film, following the 2009 movie G-Force. It was also the fifth Disney film to use Dolby 7.1 surround sound. While previous films in the Pirates of the Caribbean franchise have been filmed in the Caribbean Sea, On Stranger Tides was filmed mainly in Hawaii.

Two fishermen find a man in their nets who claims to be a member of the crew of Juan Ponce de Leon who was supposed to have died two hundred years previously while on an expedition in search of the Fountain of Youth. The man is brought before Spanish King Ferdinand VI. Ferdinand orders the head of his Secret Service, known only as The Spaniard, to find the fountain. Meanwhile in London, Joshamee Gibbs is mistaken as Jack Sparrow while being put on trial for his former captain's piracy to be hanged. However, a mysterious Judge - Sparrow in disguise - sentences Gibbs to life in prison and transfers Gibbs to jail under minimum security. During their hoped escape, having apparently given up on finding the Fountain, Sparrow reveals he came due to an imposter before he and Gibbs are arrested by crown forces. Jack is brought before King George II, who forces Jack to guide a British expedition to find the Fountain of Youth, with his guide being Captain Hector Barbossa, now a Privateer in the King's service. Barbossa reveals to Jack that he lost one of his leg and the Black Pearl. Jack reacts angrily to this before causing havoc and making his escape. He then reunites with his father, Captain Teague, who takes him into a tavern and warns Jack that the quest for the Fountain will test him. Nevertheless, Jack continues as Teague tells him of two silvery chalices needed for the Fountain, and then advises him to join a crew being gathered within the tavern.

Jack discovers that the crew is being gathered by the impostor using his name. The impostor turns out to be a former love of Jack's named Angelica. After they escape from the palace guard, Angelica drugs Jack and has him taken aboard the Queen Anne's Revenge under the command of the cruel Blackbeard. After Jack leads a failed mutiny attempt with the shanhaied crew, with the ship's cook killed off as a example to halt any future plot against himself, Blackbeard uses both a "bottled" Black Pearl and a voodoo doll in his image to force Jack to lead him to the Fountain. Blackbeard is revealed to be Angelica's father, and his quest for the fountain is to achieve eternal life so as to break a prophecy that foretells his death at the hands of a one-legged-man. Back in England, Barbossa takes Gibbs, who has memorized Jack's map before burning it, with him on theHMS Providence to find the Fountain. On the Revenge, Angelica reveals to Jack that a ritual must first take place at the fountain before one can drink from it involving Ponce de Leon's two silver chalices and a mermaid's tear. She explains that the person who drinks the chalice with the mermaid's tear will have his or her life lengthened by stealing the remaining life of whomever drinks from the other chalice. The Revenge arrives at Whitecap Bay, where Blackbeard intends to capture a mermaid. The crew are attacked by Tamara, Queen of the Mermaids, and they eventually capture a young mermaid. She catches the fancy of Philip Swift, a captive missionary, who later names her Syrena.

After setting sail to make port at safer waters, Blackbeard sends Jack to find the Santiago, Ponce de Leon's ship, to retrieve his silver chalices. Meanwhile, the Providence is destroyed by the mermaids as Barbossa, Gibbs, and a handful of men march through the jungles to find the Santiago. Finding Barbossa on the Santiago, Jack and he discover that the chalices were taken by The Spanish. Under the cover of the night, Jack and Barbossa steal the chalices from The Spaniard's tent only to be captured. While held captive, Jack has Barbossa admit that he became a privateer so he can exact revenge on Blackbeard for taking the Pearl from him. After freeing themselves and escaping with the Chalices, Jack and Barbossa devise a plan to defeat Blackbeard and then part ways. As this occurs, Syrena and Philip develop feelings for one another. Blackbeard makes it appear as if Philip is left for dead after having his throat slit. However, Philip has only been drugged, and when he awakens and returns to free Syrena, who sheds a tear of joy, which Blackbeard collects. Blackbeard takes Philip with him while leaving a heart-broken Syrena tied to a tree. The next day, Jack rejoins Blackbeard's party and hands over the silver chalices to him while regaining his compass and giving it to Gibbs.

After Blackbeard's crew arrives to the Fountain, Barbossa emerges with his men as Blackbeard realized Sparrow set up the trap. A fierce fight breaks out, and after being mortally wounded, Philip makes his way back to Syrena and frees her from her bonds. The battle ends when the Spaniard arrives with his Battalion, revealing that he came to destroy the fountain as he throws the silver chalices away before ordering his men to tear the fountain apart. Barbossa then stabs a horrified Blackbeard with his sword, which has been coated with tree frog venom. Angelica runs to her father, cutting her hand on the poisoned sword while pulling it from her father's body. Blackbeard's shanghaied crew then join Barbossa, who takes Blackbeard's sword as his own and takes his leave. Staying behind to save Angelica, Jack obtains the busted chalices from Syrena and fills them up with the fountain's last drops. Taking advantage of Blackbeard's evil nature, Jack tricks him into drinking from the wrong chalice, which saves Angelica while reducing her father into a skeleton.

As Syrena spirits Philip away into the depths, Barbossa takes command of the Queen Anne's Revenge, and renounces his oath of loyalty to Britain (even finding his old pirate hat on board the Revenge) as he sails for Tortuga. Knowing that Angelica kill him for her father's death, Jack maroons her on a deserted island with a single pistol so not to starve. Though Angelica tries to woo her way back into his graces, Jack leaves her anyway and she wastes her shot trying to kill him. Jack rejoins Gibbs, who managed to steal the bottled Pearl along with a fleet of other shrunken ships and Blackbeard's treasure. They then head off on an adventure to restore the Pearl to its original size. In a post-credits scene, Blackbeard's voodoo doll of Jack washes ashore in front of Angelica. She picks it up, and smiles as she realizes she can have her revenge.