Halfsword is a swordsmanship term.

In Medieval swordsmanship, "halfsword" usually refers to when the sword is shortened by placing a hand about half-way down the length of the sword while leaving the other on the hilt. The term is a translation of the original german "Halbenschwert." Other terms are used to mean the same thing, such as "shortened sword." Halfsword is, however, the most common term in modern use.

This is often used for leverage advantage when wrestling with the sword, as well as for delivering a more accurate and powerful thrust. Both of these are critical when fighting in plate armour, due to the fact that a slice or a cleaving blow from a sword is virtually useless against iron or steel plate. Most medieval treatises show armoured combat as consisting primarilly of fighting at the half-sword; the best options against an armoured man being a strong thrust into less protected areas such as the armpits or throat, or even better, the same against a man who has already been cast to the ground. Some weapons may have been modified specifically for this purpose. Fillipo Vadi suggests that a sword be sharp only at the tip. It has been suggested that some swords were left unsharpened in a part of the sword a hand's breadth wide about half-way down the blade in order to facilitate this technique.

In later swordsmanship, "halfsword" may also refer to a crossing of the sword in the middle of the blade.