Funayūrei (船幽霊 or 舟幽霊?, literally "boat spirit") are ghosts (yūrei) that have become vengeful spirits (onryō) at sea. They have been passed down in the folklore of various areas of Japan. They frequently appear in ghost stories and miscellaneous writings from the Edo Period as well as in modern folk customs. In the Yamaguchi Prefecture and the Saga Prefecture, they are called Ayakashi.
Funayūrei are ghosts believed to use hishaku (ladles) to fill boats with water and make them sink. They are said to be the remnants of people who have died in shipwrecks and are attempting to cause humans to join them. According to legends, there are various methods that can be used to protect from the harm they inflict, such as throwing onigiri into the sea or preparing a hishaku with its bottom missing. They are also called mōjabune (亡者船), bōko, or ayakashi depending on the area.Umibōzu, another strange phenomenon at sea, are sometimes considered to be a type of funayūrei rather a type of yōkai.
Their appearance as depicted in legends varies widely depending on the area. There are stories that speak of ghosts that appear above water, of boats that are themselves ghosts ( ghost ships), of ghosts that appear on human-occupied ships, or of any combination of the above. They are described as appearing like umibōzu or kaika. There are many legends of funayūrei at sea, but they have also been described as appearing in the rivers, lakes, and swamps of inland areas. In Kōchi Prefecture, the kechibi, a type of onibi, is also sometimes seen as being a type of funayūrei.