Shamshir (شمشیر) is the Persian word for "sword" It has come to refer to a type of sabre with a curve that is considered radical for a sword: 15 to 30 degrees from tip to tip. Although the name has been associated by popular etymology with the city of Shamshir (which in turn means "curved like the tigers nail") the word has been used to mean "sword" since ancient times, as attested by the Pahlavi word ?m?yl, and the Ancient Greek σαμψήρα (glossed as "foreign sword.")

The sword now called "shamshir" was popularized in Persia by the early 16th century, and had "relatives" in Turkey (the kilic), Mughal India (the talwar), and the ajoining Arabian world (the saif). These blades all were developed from the ubiquitous parent sword, the Turko-Mongol saber. Shamshir at times was called 'samsir'; this is usually taken to be the root of the word scimitar, though the OED considers this uncertain. Scimitar is now a more inclusive (though perhaps inaccurate) term.

The shamshir features a slim blade that has almost no taper until the very tip. Instead of being worn upright, it is worn horizontally, with the hilt and tip pointing up. It was normally used for slashing unarmored opponents either on foot or mounted; while the tip could be used for thrusting, the drastic curvature of blade made accuracy difficult. Like Japanese blades, there is no pommel and it is not quilloned, with a very small handguard. The blade was attached by a flat slab tang with rivets to the scale grip. A shamshir is a one-handled single-bladed sword.

It was similar in design to its contemporary, the Indian Talwar.