A flying wedge (also called flying V or wedge formation, or simply wedge) is a configuration created from a body moving forward in a triangular formation. This V-shaped arrangement began as a successful military strategy in ancient times when infantry units would move forward in wedge formations to smash through an enemy's lines. This principle was later used by Medieval European armies, as well as modern armed forces, which have adapted the V-shaped wedge for armored assault.

In modern times the effectiveness of flying wedge means it is still employed by civilian police services for riot control. It has also been used in some sports, although the use of wedges is sometimes banned due to the danger it poses to defenders.

The wedge (ἔμβολον, embolon in Greek; cuneus in Latin, colloquially also caput porcinum, "boar's head"), was used by both infantry and cavalry. The men deployed in a triangular or trapezoid formation with the tip leading the way. According to Arrian and Asclepiodotus, the wedge was first used by the Scythians, and then the Thracians. Philip II of Macedon adopted it from them as the main formation of his Companion cavalry and Alexander the Great faced Persian cavalry arrayed thus, as Arrian attests. The advantage of the wedge was that it offered a narrow point for piercing enemy formations and concentrated the leaders at the front. It was easier to turn than a square formation because everyone followed the leader at the apex, "like a flight of cranes".

As an infantry formation it is attested by Frontinus to have been used by the Romans in Pydna against the Macedonian line of Perseus. It was also used to great effect by the Roman legions, with the wedge proving effective in campaigns in Britain, such as during Boudicca's Revolt, where a greatly outnumbered Roman army used it to defeat the Iceni.

Keilerkopf or Keil (wild boar's head, wedge, Latin: cuneus, meaning throng) is a German phrase to describe the attack formation ("tactical body") of the prehistoric infantry of the Celts and Germanic tribes. It is generally believed that the Germanic tribes were more successful with this tactic than the Celts. It was used to force the Roman forces to split and was later applied specifically to the weakest units.

Due to the high discipline this formation required and the relatively high probability of failure, it is assumed that the front lines were filled with the best and most heavily armoured warriors of the Germanic sibbs who had to break the Roman front line.

Here the individual warrior tried to gain fame and glory in the battle. The most distinguished princes and their acolytes stood at the head of the Keil. However, this was also the most dangerous point, whence the need to be heavily armoured. But an army leader who survived a lost battle often forfeited his life (usually suicide). Warriors who had fled were hanged or slain.

According to the Roman historian Tacitus, the Keil was a tightly packed crowd, strong on all sides, not only in front and back, but also on the flanks. The formation was not like a wedge but more like a rectangle with forty warriors in the first line and 1,600 men strong. In this formation, the wingmen are at most risk. It was therefore well possible that the wing marched with some caution and held back a bit, so that the center stormed further and looked like a wedge. The outer ranks of the rear on the other hand swelled slightly. The goal was to hit hard at the same time and to drive a 40 yard wide hole into the enemy line, according to the German historian Hans Delbrück.