A shakuhachi (Japanese: 尺八; pronounced [ɕakɯhat͡ɕi]) is a Japanese longitudinal, end-blown flute that is made of bamboo. The bamboo end-blown flute now known as the shakuhachi was developed in Japan in the 16th century and is called the fuke shakuhachi (普化尺八). A bamboo flute known as the kodai shakuhachi (古代尺八, ancient shakuhachi) or gagaku shakuhachi (雅楽尺八) was derived from the Chinese xiao in the Nara period and died out in the 10th century. After a long blank period, the hitoyogiri shakuhachi (一節切尺八) appeared in the 15th century, and then in the 16th century, the fuke shakuhachi was developed in Japan. The fuke shakuhachi flourished in the 18th century during the Edo period, and eventually the hitoyogiri shakuhachi also died out. The fuke shakuhachi developed in Japan is longer and thicker than the kodai shakuhachi and has one finger hole less. It is longer and thicker than hitoyogiri shakuhachi and is superior in volume, range, scale and tone quality. Today, since the shakuhachi generally refers only to fuke shakuhachi, the theory that the shakuhachi is an instrument unique to Japan is widely accepted.

The shakuhachi is traditionally made of bamboo, but versions now exist in ABS, ebonite, anodized aluminum, and hardwoods. It was used by the monks of the Fuke Zen of Zen Buddhism in the practice of suizen (blowing meditation).

The instrument is tuned to the minor pentatonic scale.

The name shakuhachi means "1.8 shaku", referring to its size. It is a compound of two words:

Thus, the compound word shaku-hachi means "one shaku eight sun" (54.54 cm (21.47 in)), the standard length of a shakuhachi. Other shakuhachi vary in length from about 1.1 shaku up to 3.6 shaku. Although the sizes differ, all are still referred to generically as shakuhachi.

Shakuhachi are usually made from the root end of madake (Phyllostachys bambusoides) bamboo culm and are extremely versatile instruments. Professional players can produce virtually any pitch they wish from the instrument, and play a wide repertoire of original Zen music, ensemble music with koto, biwa, and shamisen, folk music, jazz, and other modern pieces.

Much of the shakuhachi's subtlety (and player's skill) lies in its rich tone colouring, and the ability for its variation. Different fingerings, embouchures and amounts of meri/kari can produce notes of the same pitch, but with subtle or dramatic differences in the tone colouring. Holes can be covered partially and pitch varied subtly or substantially by changing the blowing angle. The Honkyoku pieces rely heavily on this aspect of the instrument to enhance their subtlety and depth.

Unlike a recorder, where the player blows into a duct—a narrow airway over a block which is called a "fipple"—and thus has limited pitch control, the shakuhachi player blows as one would blow across the top of an empty bottle (though the shakuhachi has a sharp edge to blow against called utaguchi) and therefore has substantial pitch control. The term utaguchi (歌口) literally translates as "to the mouth that sings", referring to the upper and main hole of the flute where the mouthpiece or blowing edge is created by a natural diagonal cut in the bamboo.^{[citation needed]}