Arditi was the name adopted by Italian elite assault troops of World War I. The name derives from the Italian verb Ardire ("to dare") and translates as "the braves".

Reparti d'assalto (Assault Units) were formed in the summer of 1917 by Colonel Bassi, and were assigned the tactical role of shock troops, breaching enemy defenses in order to prepare the way for a broad infantry advance. The Arditi were not infantry troops, but were considered a separate combat arm, and can be considered as among the modern world's first true Special Forces.

The Reparti d'assalto were successful in bringing in a degree of movement to what had prevously been a war of entrenched positions. Their exploits on the battlefield were exemplary and they gained an illustrious place in Italian military history. They were demobilized by 1920.

The name Arditi was also used by the supporters (often war veterans) of Gabriele D'Annunzio, during his occupation of Fiume in 1919-20. Their use of a uniform with blackshirts was taken up by Benito Mussolini for his supporters, and the word Arditi then became a synonym for fascist activists.

The name is sometimes misapplied as a general term for Italian special units such as Bersaglieri.