Ultimate Fighting Championship (UFC) is a U.S.-based, male mixed martial arts (MMA) organization, and is recognized as the largest MMA promotion in the world. The UFC is headquartered in Las Vegas, Nevada and is owned and operated by Zuffa, LLC.
The UFC was started as a tournament to find the world's best fighters irrespective of their style, and was based upon Brazilian vale tudo fighting or No Holds Barred. Although there were a few limited number of rules at UFC 1, the UFC was initially known as no holds barred fighting, and contests were often violent and brutal. Early UFC fights were less sport than spectacle, which led to accusations of brutality and "human cock fighting" by opponents. Political pressures eventually led the UFC into the underground, as pay-per-view providers nixed UFC programming, nearly extinguishing the UFC's public visibility.
As political pressure mounted, the UFC reformed itself, slowly embracing stricter rules, becoming sanctioned by state athletic commissions, and marketing itself as a legitimate sporting event. Dropping the no holds barred label and carrying the banner of mixed martial arts, the UFC has emerged from its political isolation to become more socially acceptable, regaining its position in pay-per-view television.
With a cable television deal and expansion into new markets within the United States and Europe, the UFC is currently undergoing a remarkable surge in popularity, along with greater mainstream media coverage. UFC programming can now be seen on Spike TV in the United States, as well as in 35 other countries worldwide.

The UFC plans to explore new markets to host events. A date in Canada has just been announced. While other markets being considered include, Mexico, Germany, and the state of New York.
Ultimate Fighting Championship rules:
The current rules for the Ultimate Fighting Championship were originally established by the New Jersey Athletic Control Board.[28] The "Unified Rules of Mixed Martial Arts" that New Jersey established has been adopted in other states that regulate mixed martial arts, including Nevada, Louisiana, and California. These rules are also used by many other promotions within the United States, becoming mandatory for those states that have adopted the rules, and so have become the standard de facto set of rules for professional mixed martial arts across the country.
Ultimate Fighting Championship Weight divisions:
The UFC currently uses five weight classes:

- Lightweight: 146 to 155 lb (70 kg)
- Welterweight: 156 to 170 lb (77 kg)
- Middleweight: 171 to 185 lb (84 kg)
- Light Heavyweight: 186 to 205 lb (93 kg)
- Heavyweight: 206 to 265 lb (120 kg)
In addition, there are four other weight classes specified in the Unified Rules which the UFC does not currently utilize: Flyweight (under 125 lb, 57 kg), Bantamweight (126 to 135 lb, 61 kg), Featherweight (136 to 145 lb, 66 kg), and Super Heavyweight ( above 265 lb, 120 kg). The Bantamweight and Featherweight classes are used in another promotion wholly owned by Zuffa, LLC, World Extreme Cagefighting.

Source: Wikipedia