In Scottish mythology, the kelpie is a shape-shifting spirit that inhabits lakes and lochs. Its true form is a horse-like creature, but it can take on human form, as well. A story centering around this creature is a cautionary tale about the dangers of large bodies of water; people who ride on a kelpie are carried into the water and drown. Some modern depictions of the kelpie are Lighter and Softer, and instead portray them as horses with water powers.
Compare Our Hippocamps Are Different for a different kind of water horse, and Selkies And Were Seals for another deadly aquatic shapeshifter from Scottish lore. Also see Stock Ness Monster for another famous resident of the Scottish lochs, and one who is often linked to the kelpie folklore.
- Berserk: The Kelpie is one of many astral creatures that appears when Griffith's physical incarnation weakens the borders between the corporeal and spiritual worlds. It looks like a bizarre cross between a horse and a frog, and it proves to be an incredibly dangerous creature in how it controls water. Of note, it can launch balls of water as highly concussive projectiles, raise a wall of it up as a protective shield, or engulf an enemy in a massive cocoon of water to drown them in.
- Delicious in Dungeon: A Kelpie appears in Chapter 14, Kelpies resemble horses but are blue-green in colour and have a mane made of kelp, they've got a fish's tail and teeth sharp enough to crack through a giant crab's shell. The one shown is treated as a pet by Senshi, who's named it Anne. Anne unfortunately turns out not to be as tame as he thought and tries to drown and maul him the moment he tries to ride her, forcing him to put her down. As with all monsters killed by the main party, the Kelpie is cooked into several delicious meals such as a meat grill and a stew. Kelpie fat is a prized soap making ingredient and it's suggested that their internal organs can be used as makeshift flotation devices.
- Heaven's Design Team: Horse-obsessed Saturn creates a kelpie (that looks more like a hippocamp) hoping it would be accepted along with Neptune's dolphins and whales. Predictably, it's rejected. However, he later makes it smaller and it's accepted as the seahorse.
- My Little Pony: Friendship is Magic (IDW):
- The antagonist of issue 23 is a kelpie named Cassie who brainwashes all the ponies in Ponyville by singing. She looks like a hippocampus, with frill-like ears, fins instead of legs, and a mane that looks like seafoam.
- Very different kelpies appear in season 10's "The Farasian Shores" arc. They're Elemental Shapeshifters who can control water, have stripes like zebras, and live in a place based on sub-Saharan Africa.
- Fantastic Beasts: The Crimes of Grindelwald: Newt Scamander keeps a Kelpie in a tank full of sea weed. It is depicted as a gigantic legless horse-headed creature with strands of seaweed growing from its body, and Newt has managed to train it enough that it lets him ride around on its back.
- In Loch Ness (the one with Ted Danson), the monster is repeatedly referred to as a kelpie, although when it actually appears at the end it looks more like the classic plesiosaur design.
- Fantastic Beasts and Where to Find Them: Kelpies are shapeshifters whose favorite form is a horse with a mane of bulrushes. The world's most famous kelpie dwells in Loch Ness, and is the source of the Loch Ness Monster legend, as it has been observed taking the form of a giant sea serpent when viewed from a distance, but shapeshifting into an otter when Muggle tourists try to get a closer look at it.
- Modern Faerie Tales: A Kelpie appears in the first book. Kelpies here are depicted as waterhorses which trick unwitting people into coming with them and then drowning them. Kelpies can also shapeshift into more handsome forms to captivate their victims.
- The Spiderwick Chronicles: Kelpies are malign water spirits in the form of horses, with seal-like skin, cloven hooves and manes always dripping with water. They entice people into riding them in order to drown them, but can be controlled if a prospective rider manages to slip a bridle over their heads.
- In Supergirl, Lena is of Irish descent, and grew up hearing stories about kelpies, so when her mother drowned when she was a child, she believed that a kelpie was responsible. Years later, when forced to face her fears, she and Dreamer end up in a battle with a kelpie, here depicted as a liquid xenomorph-like monster.
- Jethro Tull's song "Kelpie" is sung from the perspective of a shape-shifting kelpie, taking the form of a handsome man to charm a young lady, though ultimately he plans to "steal [her] soul to the deep".
- Cardfight!! Vanguard: The Aqua Force clan has a subdivision called "Kelpie Riders" - a cavalry unit that rides Kelpies. The Kelpies in question are depicted as looking like Amazing Technicolor Wildlife horses in the front, occasionally with fins instead of ears, and the back part is a fishtail with matching colours.
- Dungeons & Dragons:
- Kelpies have appeared here and there in the game's history, making their debut in the original 1st Edition Fiend Folio. Rather than horse-like fey creatures however, they are instead evil, intelligent seaweed-like plants (kelp, get it?) able to assume other forms (usually horses or beautiful women) to lure prey to their watery graves.
- 2nd Edition Celts Campaign Sourcebook has a version much closer to the Scottish legends, the "water-horse": a Chaotic Evil, carnivorous monster which tries to drag any rider underwater by making its back magically adhesive. The actual "kelpie" is described as a more intelligent, shapeshifting variant who can take human form, but is just as nasty.
- In Pathfinder, kelpies are evil amphibious fey that assume the forms of horses or humans to lure creatures to drown and devour. Artwork of them varies however, with earlier depictions having them as horse-headed women with slimy skin, and later installments portraying them as horse-like creatures with green seaweed-like hair and skin. Filling a similar role is the water orm, a less folkloric and more cryptozoological take on Nessie-type creatures.
- Shadowrun supplement Paranormal Animals of Europe: The each-uisge is the Shadowrun equivalent of the kelpie. It is a horse-like para-animal that lives in bodies of water. It can compel metahumans to ride on its back, and secretes a glue-like substance on its skin to keep them there. It dives into the water and stays there until its rider drowns, then eats the victim's body.
- Flight Rising has kelpies as familiars. They appear similar to the classical depictions as water-themed equines, though it is unknown if they are able to shapeshift. According to their item descriptions, though, they do drown their prey, but the game's dragons are considered too large to ride kelpies and are considered to be allies instead. Kelpie manes are also in-game apparel items.
- Keldeo, the Mythical fourth member of the Swords of Justice from Pokémon Black and White, looks like a Water/Fighting unicorn that uses its horn as a sword and can blast water out of its hooves. In Pokémon Sword and Shield, it can be found in the Crown Tundra, which is based on Scotland.
- Shin Megami Tensei: Kelpie appear as demons in various entries in the franchise. In some entries they are fully horse-like, while in others the front of their body is a horse and their back half is something more aquatic, such as a mass of seaweed or a fish's tail.
- temtem: Oceara is a watery horse that looks like it's covered in seafoam. According to Denizan mythology, they're descended from the Serbatiyo who served the Sea Queen. It can only be found at the water's edge in Aguamarina Caves.
- American Dragon: Jake Long: A kelpie is depicted as an oceanic monster and the second-greatest threat to the Magical Community. It is depicted as a Fish Man which feeds off other magical creatures and then can shapeshift into their form and use their powers.
- DuckTales (2017) has a pair of kelpies named Bramble and Briar in an episode. They are generally friendly, even if they would like everyone to follow them into the water and drown. They look like My Little Phonies with wet manes and the added bonus that they're voiced by Andrea Libman (Fluttershy and Pinkie Pie) and Tara Strong (Twilight Sparkle).