Ali Baba is a fictional character, who is described in the adventure tale of Ali Baba and the Forty Thieves. It is believed by some critics that this story was added to One Thousand and One Nights by one of its European translators, Antoine Galland, who is an 18th-century French orientalist who may have heard it in oral form from a Middle Eastern story-teller from Aleppo. However, another writer and scholar Sir Richard Francis Burton said it was a part of the original One Thousand and One Nights. Most Arab and Persian(Irani) scholars seem to also agree with Burton.
Ali Baba and the Forty Thieves is a folk tale included in many versions of One Thousand and One Nights. Antoine Galland, who heard the story from Syrian Maronite storyteller Hanna Diyab, added it to the Nights in the 18th century. It is one of the most familiar of the "Arabian Nights" tales, and has been widely retold and performed in many media, especially for children, where the more violent aspects of the story are often suppressed.
Ali Baba and his older brother, Cassim, are the sons of a merchant. After their father's death, the greedy Cassim marries a wealthy woman and becomes well-to-do, building on their father's business. Ali Baba marries a poor woman and settles into the trade of a woodcutter.
One day, Ali Baba is at work collecting and cutting firewood in the forest, when he happens to overhear a group of 40 thieves visiting their stored treasure. Their treasure is in a cave, the mouth of which is sealed by a huge rock. It opens on the magic words "open sesame" and seals itself on the words "close sesame". When the thieves are gone, Ali Baba enters the cave himself and discreetly takes a single bag of gold coins home.
Ali Baba and his wife borrow his sister-in-law's scales to weigh their new wealth. Unbeknownst to them, Cassim's wife puts a blob of wax in the scales to find out what Ali Baba is using them for, as she is curious to know what kind of grain her impoverished brother-in-law needs to measure. To her shock, she finds a gold coin sticking to the scales and tells her husband. Under pressure from his brother, Ali Baba is forced to reveal the secret of the cave. Cassim goes to the cave, taking a donkey with him to take as much treasure as possible. He enters the cave with the magic words. But in his greed and excitement over the treasure, he forgets the words to get out again. The thieves find him there and kill him. When his brother does not come back, Ali Baba goes to the cave to look for him, and finds the body quartered and with each piece displayed just inside the cave's entrance, as a warning to anyone else who might try to enter.
Ali Baba brings the body home where he entrusts Morgiana, a clever slave-girl from Cassim's household, with the task of making others believe that Cassim has died a natural death. First, Morgiana purchases medicines from an apothecary, telling him that Cassim is gravely ill. Then, she finds an old tailor known as Baba Mustafa whom she pays, blindfolds, and leads to Cassim's house. There, overnight, the tailor stitches the pieces of Cassim's body back together. Ali Baba and his family are able to give Cassim a proper burial without anyone suspecting anything.
The thieves, finding the body gone, realize that another person must know their secret, and they set out to track him down. One of the thieves goes down to the town and comes across Baba Mustafa, who mentions that he has just sewn a dead man's body back together. Realizing the dead man must have been the thieves' victim, the thief asks Baba Mustafa to lead the way to the house where the deed was performed. The tailor is blindfolded again, and in this state he is able to retrace his steps and find the house. The thief marks the door with a symbol so the other thieves can come back that night and kill everyone in the house. However, the thief has been seen by Morgiana who, loyal to her master, foils the thief's plan by marking all the houses in the neighborhood similarly. When the 40 thieves return that night, they cannot identify the correct house, and their leader kills the unsuccessful thief in a furious rage. The next day, another thief revisits Baba Mustafa and tries again. Only this time, a chunk is chipped out of the stone step at Ali Baba's front door. Again, Morgiana foils the plan by making similar chips in all the other doorsteps, and the second thief is killed for his failure as well. At last, the leader of the thieves goes and looks himself. This time, he memorizes every detail he can of the exterior of Ali Baba's house.
The leader of the thieves pretends to be an oil merchant in need of Ali Baba's hospitality, bringing with him mules loaded with 38 oil jars, one filled with oil, the other 37 hiding the other remaining thieves. Once Ali Baba is asleep, the thieves plan to kill him. Again, Morgiana discovers and foils the plan, killing the 37 thieves in their oil jars by pouring boiling oil on them. When their leader comes to rouse his men, he discovers they are all dead and escapes. The next morning, Morgiana tells Ali Baba about the thieves in the jars. They bury them, and Ali Baba shows his gratitude by giving Morgiana her freedom.
To exact revenge, the leader of the thieves establishes himself as a merchant, befriends Ali Baba's son (who is now in charge of the late Cassim's business), and is invited to dinner at Ali Baba's house. However, the thief is recognized by Morgiana, who performs a sword dance with a dagger for the diners and plunges it into the thief's heart, when he is off his guard. Ali Baba is at first angry with Morgiana, but when he finds out the thief wanted to kill him, he is extremely grateful and rewards Morgiana by marrying her to his son. Ali Baba is then left as the only one knowing the secret of the treasure in the cave and how to access it.