One Thousand and One Nights (Arabic: أَلْفُ لَيْلَةٍ وَلَيْلَةٌ, Alf Laylah wa-Laylah) is a collection of Middle Eastern folktales compiled in the Arabic language during the Islamic Golden Age. It is often known in English as The Arabian Nights, from the first English-language edition (c. 1706–1721), which rendered the title as The Arabian Nights' Entertainments.

The work was collected over many centuries by various authors, translators, and scholars across West Asia, Central Asia, South Asia, and North Africa. Some tales trace their roots back to ancient and medieval Arabic, Persian, and Mesopotamian literature. Most tales, however, were originally folk stories from the Abbasid and Mamluk eras, while others, especially the frame story, are probably drawn from the Pahlavi Persian work Hezār Afsān (Persian: هزار افسان, lit. 'A Thousand Tales'), which in turn relied partly on Indian elements.

Common to all the editions of the Nights is the framing device of the story of the ruler Shahryar being narrated the tales by his wife Scheherazade, with one tale told over each night of storytelling. The stories proceed from this original tale; some are framed within other tales, while some are self-contained. Some editions contain only a few hundred nights of storytelling, while others include 1001 or more. The bulk of the text is in prose, although verse is occasionally used for songs and riddles and to express heightened emotion. Most of the poems are single couplets or quatrains, although some are longer.

Some of the stories commonly associated with the Arabian Nights—particularly "Aladdin and the Wonderful Lamp" and "Ali Baba and the Forty Thieves"—were not part of the collection in the original Arabic versions, but were instead added to the collection by French translator Antoine Galland after he heard them from Syrian writer Hanna Diyab during the latter's visit to Paris. Other stories, such as "The Seven Voyages of Sinbad the Sailor", had an independent existence before being added to the collection.

The main frame story concerns Shahryār, a king who ruled an empire that stretched from Persia to India. The story begins with Zaman, the brother of Shahryār, setting out on a journey to visit his brother at his palace. Early in the preparations, he remembers that he's left something inside his own palace, and returns to retrieve it—only to find that his wife has been making love to a black cook in their own bed. He kills them both, and continues on his journey, keeping the event a secret. Coincidentally, Shahryār finds that his own wife, as well as his numerous slave girls, have been engaging in secret orgies with black men. Shahryār has his wife killed. In his bitterness and grief, he decides that all women are the same. Shahryār begins to marry a succession of virgins only to execute each one the next morning, before she has a chance to dishonor him.

Eventually the Vizier (Wazir), whose duty it is to provide them, cannot find any more virgins. Scheherazade, the vizier's daughter, offers herself as the next bride and her father reluctantly agrees. On the night of their marriage, Scheherazade begins to tell the king a tale, but does not end it. The king, curious about how the story ends, is thus forced to postpone her execution in order to hear the conclusion. The next night, as soon as she finishes the tale, she begins another one, and the king, eager to hear the conclusion of that tale as well, postpones her execution once again. This goes on for one thousand and one nights, hence the name.

The tales vary widely: they include historical tales, love stories, tragedies, comedies, poems, burlesques, and various forms of erotica. Numerous stories depict jinn, ghouls, ape people, sorcerers, magicians, and legendary places, which are often intermingled with real people and geography, not always rationally. Common protagonists include the historical Abbasid caliph Harun al-Rashid, his Grand Vizier, Jafar al-Barmaki, and the famous poet Abu Nuwas, despite the fact that these figures lived some 200 years after the fall of the Sassanid Empire, in which the frame tale of Scheherazade is set. Sometimes a character in Scheherazade's tale will begin telling other characters a story of their own, and that story may have another one told within it, resulting in a richly layered narrative texture.

Versions differ, at least in detail, as to final endings (in some Scheherazade asks for a pardon, in some the king sees their children and decides not to execute his wife, in some other things happen that make the king distracted) but they all end with the king giving his wife a pardon and sparing her life.