Belgian National Day (Dutch: Nationale feestdag van België; French: Fête nationale belge; German: Belgischer Nationalfeiertag) is the national holiday of Belgium commemorated annually on 21 July. It is one of Belgium's ten public holidays and marks the anniversary of the investiture of King Leopold I, the country's first monarch, in 1831. Belgian National Day is celebrated in Belgium on 21 July. It is a public holiday. Historically, National Day is marked by a televised speech by the King.

The main festivities occur in Brussels. They traditionally begin with a Te Deum at the Cathedral of St. Michael and St. Gudula, attended by the King and other dignitaries. In the afternoon, the Belgian Armed Forces and police are reviewed by the King and parade around the Rue de la Loi and around the perimeter of the Brussels Park in front of the Royal Palace. Foreign contingents from Belgium's European Union and NATO allies have also participated. Refreshments and displays by Belgium's public and emergency services, armed forces, charities, and civic associations are set up for the public in the Park and nearby Place Royale, Rue de la Régence and Place Poelart. There is also a flypast by the Belgian Air Force. In the evening, there is a fireworks display. Since 2003, there has also been a concert known as the "National Ball" (bal nationale). In 2019, the festivities in Brussels were attended by an estimated 100,000 people.