The Ides of March (Latin: Idus Martii or Idus Martiae) is a day on the Roman calendar that corresponds to March 15th.

It was marked by several religious observations and became notorious as the date of the assassination of Julius Caesar in 44 BC.

The death of Caesar made the Ides of March a turning point in Roman history, as one of the events that marked the transition from the historical period known as the Roman Republic to the Roman Empire.

Although March (Martius) was the third month of the Julian calendar, in the oldest Roman calendar it was the first month of the year.

The holidays observed by the Romans from the first through the Ides often reflect their origin as new year celebrations.