Belleteyn or Beltane, sometimes known as "May Day", "May Night" or "Blossoming", takes place on the night of May Eve, the night of April 30 into May 1. It is a fertility festival beginning at dusk on the 30th and continuing until the dawn of the 1st. It is also a traditional time to begin (or end) relationships of a physical nature. Food, drink and love are the order of the evening making this celebration a time of many marriages. Bonfires abound, and revellers are encouraged to jump the flames for luck and their own fertility.
- According to one part of the framing story in The Last Wish-collection', "The Voice of Reason" , Yennefer was born on Belleteyn, and Geralt calculated that Ciri was born near the festival, too.
- Geralt meets Yennefer at a Belleteyn celebration in "Something More", one of the short stories in The Sword of Destiny.
- In the real world, this holiday corresponds with Beltaine.