Nowrūz (Persian: نوروز, IPA: [nouˈɾuːz], New Day) is the traditional ancient Iranian new year festival and also the start day of the Iranian new year.

Nowruz marks the first day of spring and the beginning of the year in Iranian calendar. It is celebrated on the day of the astronomical vernal equinox, which usually occurs on March 21 or the previous/following day depending on where it is observed. The moment the Sun crosses the celestial equator and equalizes night and day is calculated exactly every year and Iranian families gather together to observe the rituals.

The term Nowruz in writing, first appeared in Persian records in the second century AD, but it was also an important day during the time of the Achaemenids, where kings from different nations under the Persian empire used to bring gifts to the emperor also called King of Kings (Shahanshah) of Persia on Nowruz..

The UN's General Assembly in 2010 recognized the International Day of Nowruz, describing it a spring festival of Persian origin which has been celebrated for over 3,000 years. During the meeting of The Inter-governmental Committee for the Safeguarding of the Intangible Heritage of the United Nations, held between 28 September – 2 October 2009 in Abu Dhabi, Nowrūz was officially registered on the UNESCO List of the Intangible Cultural Heritage of Humanity. Since 2010, the United Nations General Assembly recognizes March 21 as the "International Day of Nowruz".