A frame story (also known as a frame tale, frame narrative, sandwich narrative, or intercalation) is a literary technique that serves as a companion piece to a story within a story, where an introductory or main narrative sets the stage either for a more emphasized second narrative or for a set of shorter stories. The frame story leads readers from a first story into one or more other stories within it. The frame story may also be used to inform readers about aspects of the secondary narrative(s) that may otherwise be hard to understand. This should not be confused with narrative structure. Notable examples are the 1001 Nights and The Decameron.

Some of the earliest frame stories are from ancient Egypt, including one in the Papyrus Westcar, the Tale of the Shipwrecked Sailor, and The Eloquent Peasant. Other early examples are from Indian literature, including the Sanskrit epics Mahabharata, Ramayana, Panchatantra, Syntipas's The Seven Wise Masters, and the fable collections Hitopadesha and Vikram and The Vampire. This form gradually spread west through the centuries and became popular, giving rise to such classic frame tale collections as the One Thousand and One Nights (Arabian Nights), The Decameron, and the Canterbury Tales, in which each pilgrim tells his own kind of tale, and whose frame story "was once the most admired part of Chaucer's work".

The use of a frame story in which a single narrative is set in the context of the telling of a story is also a technique with a long history, dating back at least to the beginning section of Homer's Odyssey, in which the narrator Odysseus tells of his wandering in the court of King Alcinous.

A frame story is a literary device that acts as a convenient conceit to organize a set of smaller narratives, either devised by the author or taken from a previous stock of popular tales, slightly altered by the author for the purpose of the longer narrative. Sometimes a story within the main narrative encapsulates some aspect of the framing story, in which case it is called a mise en abyme.

A typical frame story is One Thousand and One Nights, in which the character Scheherazade narrates a set of fairy tales to the Sultan Shahriyar over many nights. Many of Shahrazad's tales are also frame stories, such as Tale of Sindbad the Seaman and Sindbad the Landsman, a collection of adventures related by Sindbad the Seaman to Sindbad the Landsman.

Ovid's Metamorphoses makes extensive use of framing, with the stories nested several deep, allowing the inclusion of many different tales in one work. Emily Brontë's Wuthering Heights uses this literary device to tell the story of Heathcliff and Catherine, along with the subplots. Her sister Anne uses this device in her epistolary novel The Tenant of Wildfell Hall. The main heroine's diary is framed by the narrator's story and letters.

Mary Shelley's novel Frankenstein has multiple framed narratives. In the book, Robert Walton writes letters to his sister, describing the story told to him by the scientist Victor Frankenstein. Midway through Frankenstein's story, he is met by the monster, who tells him his own story after he was created, and this third narrative even briefly contains the tale of a family whom he had been observing. This set of frame narratives that fit together is sometimes called a Chinese box narrative; other instances of this style of narrative can be found in Plato's Symposion, Jostein Gaarder's The Solitaire Mystery, Emily Brontë's Wuthering Heights, and Joseph Conrad's Heart of Darkness.

Frame stories have appeared in comic books. Neil Gaiman's comic book series The Sandman featured a story arc called Worlds End which consisted of frame stories, and sometimes even featured stories within stories within stories.