Onibi is a type of atmospheric ghost light in legends of Japan. According to folklore, they are the spirits born from the corpses of humans and animals. They are also said to be resentful people that have become fire and appeared. Also, sometimes the words "will-o'-wisp" or "jack-o'-lantern" are translated into Japanese as "onibi".

Atmospheric ghost lights are lights that appear in the atmosphere without an obvious cause. Examples include the onibi, hitodama and will-o'-wisp. They are often seen in humid climates.