Koninginnedag or Queen's Day is a national holiday in the Kingdom of the Netherlands. Celebrated on 30 April (the 29th if the 30th falls on a Sunday), Koninginnedag is Queen Beatrix's official birthday.

Though Queen Beatrix was born on 31 January, the holiday is observed on 30 April as it was the birthday of her mother and predecessor, Juliana.

Many of the traditional activities are held outside, and observing the holiday in April makes suitable weather more likely.