is a traditional slub-woven silk fabric from Japan. It is a tabby weave material woven from yarn produced using silk noil, short-staple silk fibre (as opposed to material produced using longer, filament yarn silk fibres). The short silk fibres are degummed and, traditionally, the yarns are hand-joined to form a continuous length before weaving, a technique also used for cheaper bast fibres. Yarns are joined by twisting the ends to be joined in the same direction, then twisting both ends, bundled together, in the other direction, to make a two-ply yarn at the overlap. It might alternately be loosely handspun, with few twists per unit length. Because of this structure, is rough-surfaced, soft and drapey, softening further with age.
Between 1910 and 1925 (late Taishà  to Shà Âwa era), it became common to spin as well as weave silk noil by machine (see for the technological developments that made this possible). This machine-spun cloth largely displaced as one of the cheapest silk fabrics. Prices dropped drastically, and silk materials and clothing was suddenly within the budget of most Japanese; stores also began to sell off-the-peg, ready-to-wear kimono at about this time.
Originally, was homemade from domestic or wild-gathered silkworm cocoons that had been broken by hatching or were irregularly formed. Unlike the long-fiber silk, such cloth was permitted to peasants. Traditionally a peasant cloth, handmade is very labour-intensive to produce, and has become expensive over time, valued as a luxury folk-craft.
The term tsumugi is broadly used to describe many types of casual woven kimono, even if they do not use tsumugi silk. One of the most famous examples is à Âshima-tsumugi, which though is considered a tsumugi is not made with tsumugi thread. Additionally, cotton kimono with fine kasuri patterns are considered to be tsumugi.
was originally a homespun textile, produced using silk fibre deemed unusable for the production of finer fabrics, and many regional variations existed. Some of these regional variations still exist today and are recognized as , famous products of their place of origin.