A cloak of invisibility is an item that prevents the wearer from being seen. In folklore, mythology and fairy tales, a cloak of invisibility appears either as a magical item used by duplicitous characters or an item worn by a hero to fulfill a quest. It is a common theme in Welsh mythology and Germanic folklore, and may originate with the cap of invisibility seen in ancient Greek myths. The motif falls under "D1361.12 magic cloak of invisibility" in the Stith Thompson motif index scheme.

Cloaks of invisibility are magical items found in folklore and fairy tales. Such cloaks are common in Welsh mythology; a "Mantle of Invisibility" is described in the tale Culhwch and Olwen (c. 1100) as one of King Arthur's most prized possessions. The mantle is described again, and in more detail, in the Breuddwyd Rhonabwy, and is later listed as one of the Thirteen Treasures of the Island of Britain. A similar mantle appears in the Second Branch of the Mabinogi, in which it is used by Caswallawn to assassinate the seven stewards left behind by Bran the Blessed and usurp the throne.

In the English fairy tale Jack the Giant Killer, the hero is rewarded with several magical gifts by a giant he has spared, among them a coat of invisibility. Iona and Peter Opie observe in The Classic Fairy Tales (1974), that Jack's coat may have been borrowed from the Tale of Tom Thumb or from Norse mythology, but they also draw comparisons with the Celtic stories of the Mabinogion.

The counterpart in Japan is the kakuremino (隠れ蓑), a magical "straw cape" or "raincoat" of invisibility. In the folktale of the "Peach Boy" Momotarō, one of the treasures the hero collects from the ogres is a cape of invisibility, paralleling the story of Jack the giant-slayer.

Although occurrences in fairy tales are rare, the cloak of invisibility appears in the German tale The Twelve Dancing Princesses (KHM 133) and in The King of the Golden Mountain (KHM 92) in Grimm's Fairy Tales. The cloak in German fairy tales may be traceable to the tarnkappe ("cloak of concealment"), such as the one that the hero Sîfrit (Siegfried) acquires from the dwarf Alberich in the Middle High German epic Nibelungenlied. The Grimms clarify that Sîfrit's kappe is a cape that covers not just the head but enshrouds the body, though in later times tarnkappe came to be regarded as a cap of invisibility. The tarnkappe (or tarnkeppelin) is also owned by the dwarf king who is the title character in Laurin. In different passages or variant manuscripts of these works, the tarnkappe is also referred to as the tarnhût (mod. Ger. Haut "skin") or hehlkappe (mod. Ger. hehlen "to hide").

In the original epic Nibelungenlied, the hero's cloak not only grants him invisibility, but also increases his strength, to win over the Icelandic queen Brünhild. In Richard Wagner's opera cycle Der Ring des Nibelungen, the cloak becomes a magic helmet called the Tarnhelm, which also imparts the ability to transform upon its wearer. When Fritz Lang adapted Nibelungenlied for the movie screen in his 1924 film Die Nibelungen, Siegfried uses a veil or net of invisibility gained from the dwarf Alberich.^{[citation needed]}

Raoul Walsh's film The Thief of Bagdad, was released in the same year as Die Nibelungen and also features a cloak of invisibility playing a pivotal role.^{[citation needed]}

Edgar Rice Burroughs uses the idea of an invisibility cloak in his 1931 novel A Fighting Man of Mars. The movie Erik the Viking humorously depicts the title character using a cloak of invisibility, which he does not realize apparently works only on elderly men. In The Lord of the Rings, Frodo, and the other members of the Fellowship of the Ring, were given cloaks by the Elves, and Samwise asked, "Are these magic cloaks?" The cloak given to Frodo camouflaged him so that the enemy could see "nothing more than a boulder where the Hobbits were."^{[citation needed]}