Koto is a traditional Japanese stringed musical instrument which shares a common ancestor with the modern Chinese guzheng. The koto is the national instrument of Japan. Koto are about 180 centimetres (71 in) width, and made from kiri wood (Paulownia tomentosa). They have 13 strings that are strung over 13 movable bridges along the width of the instrument. Players can adjust the string pitches by moving these bridges before playing, and use three finger picks (on thumb, index finger, and middle finger) to pluck the strings.

One of the characters for koto, is also read as sô in certain contexts. Though often called by a number of other names, these terms almost always refer to similar, but different instruments, such as the Chinese guzheng or guqin ( called kin in Japanese).