April Fools' Day or April Fool's Day (sometimes called All Fools' Day) is an annual (primarily) Western celebration commemorated on April 1 by playing practical jokes and spreading hoaxes. The jokes and their victims are called April fools. People playing April Fool jokes often expose their prank by shouting "April fool(s)" at the unfortunate victim(s). Some newspapers, magazines and other published media report fake stories, which are usually explained the next day or below the news section in smaller letters. Although popular since the 19th century, the day is not a public holiday in every country.

Aside from April Fools' Day, the custom of setting aside a day for the playing of harmless pranks upon one's neighbour has historically been relatively common in the world.