Also known as Three Kings' Day, the Feast of the Epiphany commemorates the arrival of the Magi in Bethlehem to honour the baby Jesus 12 days after his birth.
The day has been a public holiday in Poland since 2011, when it was reinstated after a hiatus of more than five decades.
This year's celebrations will feature colourful processions in around 1,000 cities and towns nationwide, state news agency PAP reported.
In the capital Warsaw, President Karol Nawrocki and First Lady Marta Nawrocka are expected to join the celebrations.
The day also marks the beginning of the Carnival season, which lasts until the Tuesday before Ash Wednesday.
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Source: IAR, PAP