The Hijri New Year, also known as Islamic new year (Arabic: رأس السنة الهجرية‎ Ras as-Sanah al-Hijriyah) is the day that marks the beginning of a new Islamic calendar year, and is the day on which the year count is incremented. The first day of the year is observed on the first day of Muharram, the first month in the Islamic calendar.

The event also commemorates the death of Mohammed’s grandson Imam Hussein who, along with his family and followers, was martyred in the battle of Karbala in 680 which took place on the tenth day of the month of Muharram. This is celebrated by Shia Muslims with public enactments of grief. Sunni Muslims celebrate the day according to the Sunnah of Mohammed. Finding some Jews fasting on this day, he enquired of them why they fasted. They replied that it was in honor of Moses. Mohammed then said that Islam honored Moses more highly and established a two day fast for Muharram. This fast was in effect before the martyrdom of Imam Hussein.

Since the Islamic year is 11 to 12 days shorter than the Gregorian year, the Islamic new year does not come on the same day of the Gregorian calendar every year (see Islamic calendar). While some Islamic organizations prefer determining the new month (and hence the new year) dates by local sighting of the moon, most Islamic institutions and countries, including Saudi Arabia, follow astronomical calculations to determine future dates of the Islamic calendar.

New Year is the time at which a new calendar year begins and the calendar's year count is incremented. In many cultures, the event is celebrated in some manner. The New Year of the Gregorian calendar, today in worldwide use, falls on 1 January, as was the case with the Roman calendar. There are numerous calendars that remain in regional use that calculate the New Year differently.

The order of months in the Roman calendar was January to December since King Numa Pompilius in about 700 BC, according to Plutarch and Macrobius. According to Catholic tradition, 1 January is the day of the circumcision of Jesus (on the eighth day from his birth), when the name of Jesus was given to him (Luke 2:21).

It was only relatively recently that 1 January again became the first day of the year in Western culture. Until 1751 in England and Wales (and all British dominions) the new year started on 25 March – Lady Day, one of the four quarter days (the change to 1 January took place in 1600 in Scotland). Since then, 1 January has been the first day of the year. During the Middle Ages several other days were variously taken as the beginning of the calendar year (1 March, 25 March, Easter, 1 September, 25 December).^{[citation needed][where?]} In many countries, such as the Czech Republic, Italy and the UK, 1 January is a national holiday.