Sumo (相撲 sumō?) is a competitive full-contact wrestling sport where a rikishi (wrestler) attempts to force another wrestler out of a circular ring (dohyō) or into touching the ground with anything other than the soles of the feet. The characters 相撲 literally mean "striking one another".

The sport originated in Japan, the only country where it is practiced professionally. It is generally considered to be a gendai budō (a modern Japanese martial art), though this definition is misleading as the sport has a history spanning many centuries. Many ancient traditions have been preserved in sumo, and even today the sport includes many ritual elements, such as the use of salt purification, from the days when sumo was used in the Shinto religion. Life as a wrestler is highly regimented, with rules laid down by the Japan Sumo Association. Most sumo wrestlers are required to live in communal "sumo training stables", known in Japanese as heya, where all aspects of their daily lives—from meals to their manner of dress—are dictated by strict tradition.

n addition to its use as a trial of strength in combat, sumo has also been associated with Shinto ritual, and even certain shrines carry out forms of ritual dance where a human is said to wrestle with a kami (a Shinto divine spirit); see Shinto origins of sumo. It was an important ritual at the imperial court. Representatives of each province were ordered to attend the contest at the court and fight. They were required to pay for their travels themselves. The contest was known as sumai no sechie, or "sumai party."

Cross-influence from other nations adjacent to Japan, sharing many cultural traditions, cannot be ruled out, as they also feature styles of traditional wrestling that bear resemblance to sumo. Notable examples include Mongolian wrestling, Chinese Shuai jiao, and Korean Ssireum.

Over the rest of Japanese recorded history, sumo's popularity has changed according to the whims of its rulers and the need for its use as a training tool in periods of civil strife. The form of wrestling combat probably changed gradually into one where the main aim in victory was to throw one's opponent. The concept of pushing one's opponent out of a defined area came some time later.

Also, it's believed that a ring, defined as something other than simply the area given to the wrestlers by spectators, came into being in the 16th century as a result of a tournament organized by the then principal warlord in Japan, Oda Nobunaga. At this point wrestlers would wear loose loincloths, rather than the much stiffer mawashi wrestling belts of today. During the Edo period, wrestlers would wear a fringed decorative apron called a kesho-mawashi during the bout, whereas today these are worn only during pre-tournament rituals. Most of the rest of the current forms within the sport developed in the early Edo period.

Professional sumo (大相撲 ōzumō?) can trace its roots back to the Edo period in Japan as a form of sporting entertainment. The original wrestlers were probably samurai, often rōnin, who needed to find an alternative form of income. Current professional sumo tournaments began in the Tomioka Hachiman Shrine in 1684, and then were held in the Ekō-in in the Edo period. Western Japan also had its own sumo venues and tournaments in this period with by far the most prominent center being in Osaka. Osaka sumo continued to the end of the Taishō period in 1926, when it merged with Tokyo sumo to form one organization. For a short period after this four tournaments were held a year, two tournaments in locations in western Japan such as Nagoya, Osaka and Fukuoka, and two in the Ryōgoku Kokugikan in Tokyo. From 1933 onward tournaments were held almost exclusively in the Ryōgoku Kokugikan until the American occupation forces appropriated it and the tournaments were moved to Meiji Shrine until the 1950s. Then an alternate location, the Kuramae Kokugikanwhich was near Ryōgoku, was built for sumo. Also in this period, the Sumo Association began expanding to venues in western Japan again, reaching a total of six tournaments a year by 1958 with half of them in Kuramae. In 1984, the Ryōgoku Kokugikan was rebuilt and sumo tournaments in Tokyo have been held there ever since.

Winning a sumo bout
The winner of a sumo bout is either:

The first wrestler to force his opponent to step out of the ring.
The first wrestler to force his opponent to touch the ground with any part of his body other than the bottom of his feet.


There are also a number of other less common rules that can be used to determine the winner. For example, a wrestler using an illegal technique (or kinjite) automatically loses, as does one whose mawashi (or belt) becomes completely undone. A wrestler failing to turn up for his bout (including through a prior injury) also automatically loses (fusenpai).

Matches consist solely of a single round and often last only a few seconds, as usually one wrestler is quickly ousted from the circle or thrown to the ground. However, they can occasionally last for several minutes. Each match is preceded by an elaborate ceremonial ritual. Traditionally, sumo wrestlers are renowned for their great girth and body mass which is often a winning factor in sumo. There are no weight divisions in professional sumo, and considering the range of body weights in sumo, an individual wrestler can sometimes face an opponent twice his own weight. However, with superior technique, smaller wrestlers can control and defeat much larger opponents.[4]

After the winner is declared, an off-stage gyōji (or referee) determines the kimarite (or winning technique) used in the bout, which is then announced to the audience.

On rare occasions the referee or judges may award the win to the wrestler who touched the ground first; this happens if both wrestlers touch the ground at very nearly the same time and it is decided that the wrestler who touched the ground second had no chance of winning as, due to the superior sumo of his opponent, he was already in an irrecoverable position. The losing wrestler is referred to as being shini-tai(“dead body”) in this case.

Wrestling ring (dohyō)
Sumo matches take place in a dohyō (土俵): a ring, 4.55 metres (14.9 ft) in diameter and 16.26 square metres (175.0 sq ft) in area, of rice-straw bales on top of a platform made of clay mixed with sand. A newdohyō is built for each tournament by the bout callers (or yobidashi). At the center are two white lines, the shikiri-sen, behind which the wrestlers position themselves at the start of the bout.[5] A roof resembling that of a Shinto shrine may be suspended over the dohyō.

Professional sumo
 
Sumo wrestlers gather in a circle around the gyōji (referee) in the dohyō-iri (ring-entering ceremony).
Professional sumo is organized by the Japan Sumo Association.[6] The members of the association, called oyakata, are all former wrestlers, and are the only people entitled to train new wrestlers. All practicing wrestlers are members of a training stable (or heya) run by one of the oyakata, who is the stablemaster for the wrestlers under him. Currently there are 43 training stables for about 660 wrestlers.[7]

All sumo wrestlers take wrestling names called shikona (四股名?), which may or may not be related to their real names. Often wrestlers have little choice in their name, which is given to them by their trainer (or stablemaster), or by a supporter or family member who encouraged them into the sport. This is particularly true of foreign-born wrestlers. A wrestler may change his wrestling name during his career, with some wrestlers changing theirs several times.[6]

Sumo wrestling is a strict hierarchy based on sporting merit. The wrestlers are ranked according to a system that dates back to the Edo period. Wrestlers are promoted or demoted according to their performance in six official tournaments held throughout the year. A carefully preparedbanzuke listing the full hierarchy is published two weeks prior to each sumo tournament.[8]

In addition to the professional tournaments, exhibition competitions are held at regular intervals every year in Japan, and approximately once every two years the top ranked wrestlers visit a foreign country for such exhibitions. None of these displays is taken into account in determining a wrestler's future rank. Rank is determined only by performance in Grand Sumo Tournaments (or honbasho), which are described in more detail below.[5]