Terror is a pronounced state of fear, an overwhelming sense of imminent danger.

• For the parasomnia sleep disorder, see night terror.
• For the period of the French Revolution, see its more formal name, the Reign of Terror.
• For campaigns of political terror during the Russian Revolution of 1917, see Red Terror and White Terror. A later campaign, sometimes referred to as the Great Terror, is discussed in the article Great Purge.
• For historical and popular terms referring to violence (especially against civilians, whether prominent or not) that is insignificant in terms of military tactics but aimed at undermining morale, see terrorism.
• For the USA's "War on Terror" (2001–present), see War on Terrorism.
• Eight ships of the Royal Navy have been named HMS Terror.
• For the Californian hardcore band, see Terror (band).
• Two mountains have been named Mount Terror, one in Antarctica, and one in the USA.
• For extreme style of techno music see terrorcore.