Dyngus Day, sometimes spelled Dingus Day, is a holiday that is celebrated in Poland as well as in some Polish communities in the United States. This holiday always takes place on Easter Monday and it's meant to be a fun, light-hearted holiday. It is also called Wet Monday as the tradition of Dyngus Day is for males to soak females with water from buckets, hoses and the like. Traditionally, the females are supposed to get their revenge on Tuesday by throwing dishes, but now most females just soak the men back with water on the same day.

The history of the holiday dates back to the Easter Monday 966 A.D. baptism of the Polish prince Mieszko I. This was a significant baptism because it was taken by the Polish people to mean that all of Poland was Christian. Since baptism is thought to relate to purification, cleansing and fertility, the idea somehow adapted into Dyngus Day and boys soaking girls with water. Water traditions also relate to the mass Lithuanian baptisms that took place after the Lithuanian Duke, Jagiello, and the Polish Queen, Jadwiga, were married.

Dyngus Day is meant as a fun holiday after the serious period of Lent. The actual Easter Monday act of soaking a person with water and/or hitting him or her with switches of pussy willows is called Smigus Dyngus. Originally, Smigus Dyngus referred to a sort of trick-or-treating tradition that has mostly died out in urban areas. It involved the use of a special cart and rooster brought to each house in order to collect food and drink. The rooster was either real or carved from wood.

Still another legend associated with Dygnus Day is one that remembers a Polish Princess named Wanda. The use of water to soak females is said to remember Wanda as she chose to drown herself in the Wilsa River rather than marry a man she didn't love. Religiously, Dyngus Day marks the start of Polish Catholicism.