Obi is the Japanese word for belt, and in a martial arts context it refers to the belt tied around a gi jacket to hold it closed. Beyond its practical role, the obi is one of the clearest visible markers of a student's progress, since its colour commonly indicates rank, moving from white through a sequence of colours toward black in many schools.
Obi width, thickness and material vary with the art and with rank: a beginner's belt is typically a simple cotton strip, while a well worn black belt in judo or karate is often thicker and stiffer than a new one, since older belts are traditionally kept rather than replaced as they fray. How a belt is tied is itself something taught early on, usually with a square knot that keeps both ends even and stays secure through movement. Colour systems are not standardised internationally, so the belt colour used for a given grade can differ from one school or federation to another.
See our belt guide and tying instructions for step by step folding, and the entries on kyu grades and dan grades for how ranking systems are structured.
