A mermaid is a legendary aquatic creature with the head and upper body of a female human and the tail of a fish.[1] Mermaids appear in the folklore of many cultures worldwide, including the Near East, Europe, Africa and Asia. The first stories appeared in ancient Assyria, in which the goddess Atargatis transformed herself into a mermaid out of shame for accidentally killing her human lover. Mermaids are sometimes associated with perilous events such as floods, storms, shipwrecks and drownings. In other folk traditions (or sometimes within the same tradition), they can be benevolent or beneficent, bestowing boons or falling in love with humans.

The male equivalent of the mermaid is the merman, also a familiar figure in folklore and heraldry. Although traditions about and sightings of mermen are less common than those of mermaids, they are generally assumed to co-exist with their female counterparts.

Some of the attributes of mermaids may have been influenced by the Sirens of Greek mythology. Historical accounts of mermaids, such as those reported by Christopher Columbus during his exploration of the Caribbean, may have been inspired by manatees and similar aquatic mammals. While there is no evidence that mermaids exist outside of folklore, reports of mermaid sightings continue to the present day, including 21st century examples from Israel and Zimbabwe.

Mermaids have been a popular subject of art and literature in recent centuries, such as in Hans Christian Andersen's well-known fairy tale "The Little Mermaid" (1836). They have subsequently been depicted in operas, paintings, books, films and comics.