Omens or portents are signs encountered fortuitously that are believed to foretell the future. Their interpretation is a form of divination.

The augur and haruspex of ancient Rome were professional readers of omens. The augurs tried to read the future in the flight of birds. The haruspex sought omens in the entrails of sacrificed animals.

In astrology both new and old, eclipses (whether solar or lunar) are thought to be omens of significant events, births, or other important developments that are occuring or about to occur. The course of Diana's life is a remarkable example of a life touched very powerfully by these celestial alignments.

For example, a solar eclipse occurred only one day after Princess Diana and Prince Charles were married on July 29, 1981. Next, their firstborn son Prince William, the future King of England, was born slightly over a year later only a few hours after a solar eclipse occurred on June 21, 1982. Ten and a half years later, Princess Diana and Prince Charles were formally seperated on December 9, 1992, the exact day of a lunar eclipse. Finally, Princess Diana died in a car crash in Paris on August 31, 1997, only one day before a solar eclipse occurred.

Other omens are less subject to putting into a system, and are not voluntarily sought. The superstition that if you break a mirror you will suffer seven years of bad luck is an example of such an omen.

• The Omen (1976) was a horror film starring Gregory Peck.
• Omen is also an Heavy Metal band from the US; see Omen (band)
• Omen is also a comedy character played by Italian showman Raul Cremona