Mixed martial arts (MMA) is a full-contact fighting sport based on striking and grappling, incorporating techniques from various combat sports from around the world.

In the early 20th century, various inter-stylistic contests took place throughout Japan and the countries of East Asia. At the same time, in Brazil there was a phenomenon called vale tudo, which became known for unrestricted fights between various styles such as judo, Brazilian jiu-jitsu, catch wrestling, luta livre, Muay Thai and capoeira. An early high-profile mixed bout was Kimura vs Gracie in 1951. In mid-20th-century Hong Kong, rooftop street fighting contests between different martial arts styles gave rise to Bruce Lee's hybrid martial arts style, Jeet Kune Do. Another precursor to modern MMA was the 1976 Ali vs. Inoki exhibition bout, fought between boxer Muhammad Ali and wrestler Antonio Inoki in Japan, where it later inspired the foundation of Shooto in 1985, Pancrase in 1993, and the Pride Fighting Championships in 1997.

In the 1990s, the Gracie family brought their Brazilian jiu-jitsu style, first developed in Brazil from the 1920s, to the United States—which culminated in the founding of the Ultimate Fighting Championship (UFC) promotion company in 1993. The company held an event with almost no rules, mostly due to the influence of Art Davie and Rorion Gracie attempting to replicate mixed contests that existed in Brazil and Japan. They would later implement a different set of rules (example: eliminating kicking a grounded opponent), which differed from other leagues which were more in favour of realistic, "street-like" fights. The first documented use of the term mixed martial arts was in a review of UFC 1 by television critic Howard Rosenberg in 1993.

Originally promoted as a competition to find the most effective martial arts for real unarmed combat, competitors from different fighting styles were pitted against one another in contests with relatively few rules. Later, individual fighters incorporated multiple martial arts into their style. MMA promoters were pressured to adopt additional rules to increase competitors' safety, to comply with sport regulations and to broaden mainstream acceptance of the sport. Following these changes, the sport has seen increased popularity with a pay-per-view business that rivals boxing and professional wrestling.

In ancient China, combat sport appeared in the form of Leitai, a no-holds-barred mixed combat sport that combined Chinese martial arts, boxing and wrestling.

In ancient Greece, there was a sport called pankration, which featured grappling and striking skills similar to those found in modern MMA. Pankration was formed by combining the already established wrestling and boxing traditions and, in Olympic terms, first featured in the 33rd Olympiad in 648 BC. All strikes and holds were allowed with the exception of biting and gouging, which were banned. The fighters, called pankratiasts, fought until someone could not continue or signaled submission by raising their index finger; there were no rounds. According to the historian E. Norman Gardiner, "No branch of athletics was more popular than the pankration." There is also evidence of similar mixed combat sports in ancient Egypt, India and Japan.

The mid-19th century saw the prominence of the new sport savate in the combat sports circle. French savate fighters wanted to test their techniques against the traditional combat styles of its time. In 1852, a contest was held in France between French savateurs and English bare-knuckle boxers in which French fighter Rambaud alias la Resistance fought English fighter Dickinson and won using his kicks. However, the English team still won the four other match-ups during the contest. Contests occurred in the late 19th to mid-20th century between French savateurs and other combat styles. Examples include a 1905 fight between French savateur George Dubois and a judo practitioner Re-nierand which resulted in the latter winning by submission, as well as the highly publicized 1957 fight between French savateur and professional boxer Jacques Cayron and a young Japanese karateka named Mochizuki Hiroo which ended when Cayron knocked Hiroo out with a hook.

Catch wrestling appeared in the late 19th century, combining several global styles of wrestling, including Indian pehlwani and English wrestling. In turn, catch wrestling went on to greatly influence modern MMA.^{[citation needed]} No-holds-barred fighting reportedly took place in the late 1880s when wrestlers representing the style of catch wrestling and many others met in tournaments and music-hall challenge matches throughout Europe. In the US, the first major encounter between a boxer and a wrestler in modern times took place in 1887 when John L. Sullivan, then heavyweight world boxing champion, entered the ring with his trainer, wrestling champion William Muldoon, and was slammed to the mat in two minutes. The next publicized encounter occurred in the late 1890s when future heavyweight boxing champion Bob Fitzsimmons took on European wrestling champion Ernest Roeber. In September 1901, Frank "Paddy" Slavin, who had been a contender for Sullivan's boxing title, knocked out future world wrestling champion Frank Gotch in Dawson City, Canada. The judo-practitioner Ren-nierand, who gained fame after defeating George Dubois, would fight again in another similar contest, which he lost to Ukrainian Catch wrestler Ivan Poddubny.