A katana is a type of Japanese sword and often it is called a "samurai sword". The term katana may be applied to any curved Japanese sword with a blade length of greater than 60 cm. The term is sometimes incorrectly used as a generic name for all the Japanese swords. The katana is characterized by its distinctive appearance. It is a sword with a curved, slender, single edged blade, circular or squared guard, and long grip to accommodate two hands. Historically, it has become inseparable from image of the samurai warriors of feudal Japan, and has become renowned for its extraordinary sharpness and cutting ability. Indeed, in modern Western popular culture, the purported capabilities of the katana have far exceeded its real life characteristics and limitations.

The katana sword originated in the Muromachi period (1392–1573), as a result of rapidly changing battle conditions requiring faster response times from the warriors who fought in close combat with cold weapons. The katana was worn with the blade facing up, which allowed the samurai to draw and cut their enemy in a single motion, while previously, the curved sword of the samurai was worn with the blade facing down. The length of the katana's blade varied considerably during the course of its history from the 60 cm shorter blades to a bit longer 73 cm. The katana was also often paired with a smaller sword and both were worn by the members of the warrior class. The two weapons together were called the daishō and represented the social power and personal honour of the samurai warrior and his family.

The legitimate Japanese sword katana is made only from the Japanese steel "Tamahagane". The katana gets its gentle curve from quenching during forming and it is actually straight prior to the quenching. The forging of a Japanese blade typically took hours or days, and was considered a sacred art. As with many complex endeavors, several artists were involved rather than only one. It is thus fair to say that katana construction was actually quite a hard labour intensive bladesmithing process. Traditional samurai katana swords are still made in Japan and occasionally elsewhere and they are termed "shinsakuto", and can be very expensive due to the difficulty of their construction. These are not considered reproductions as they are made by traditional techniques and from traditional materials used in the old feudal Japan. After it is forged the sword blade is decorated with different designs and markings, and then polished to complete its construction. The polishing process almost always takes longer than crafting, and a good polish can greatly improve the beauty of a blade, while a bad one can completely ruin even the best of blades.

It is very important to handle the katana sword apropriately so it would not get permanently damaged. If mishandled in its storage or maintenance, the katana sword may become seriously damaged and lose all its value and quality. It is extremely important that the blade of the sword remain well oiled and that it is regulary polished, as the natural moisture residue from the hands of the user will rapidly cause the blade to rust if not cleaned off. When stored for longer periods, it is likewise important that the sword blade be checked frequently and aired out if necessary to prevent rust or mold from forming.

The katana sword is an everlasting symbol of Japan and its long warrior tradition represented through the samurai. It is today considered to be a valuable item for any weapons and antiques collection.