A Kallikantzaros (Καλλικάντζαρος) pl. Kallikantzaroi is a malevolent goblin in Greek folk tradition. They dwell underground but come to the surface from 25 December to 6 January (from the winter solstice for a fortnight during which time the sun ceases its seasonal movement).

It is believed that Kallikantzaroi stay underground sawing the World tree, so that it will collapse, along with Earth. However, when they are about to saw the final part, Christmas dawns and they are able to come to surface. So they forget the Tree and come to bring trouble to mortals.

Finally, on the Epiphany (6th January), the sun starts moving again, and they must go underground again to continue their sawing. And then they see that during their absence the World tree has healed itself, so they must start working all over again. This happens every year.

There is no standard appearance of Kallikantzaroi, but some Greeks have imagined them with some animal parts, like: human but hairy body, horse legs, boar tusks etc. However there are some standard characters in the tales like the King, the Queen, one who had 3 legs and others.

There were also some ways so that the people would protect themselves during the days when the Kallikantzaroi were loose. For example they could leave a colander on their doorstep: if a Kallikantzaros approached for his evildoings, he would rather sit and count all the holes till the sunrise, when he was supposed to hide. The Kallikantzaroi also could not count above 2, since 3 is a holy number, and by pronouncing it, they would kill themselves.

Legend has it that any child born during the twelve days of the Saturnalia (17th through 23rd of December) was in danger of becoming a Kallikantzaros. The antidote: Binding the baby in tresses of garlic or straw, or singeing the child's toenails.

In Greek language Kallikantzaros is also used for every short, ugly and usually mischievous being. If not used for the abovementioned creatures, it seems to express the collective sense for the English words leprechaun, gnome and goblin.