UFC 146: Dos Santos vs. Mir was a mixed martial arts (MMA) pay-per-view event (PPV) promoted by the Ultimate Fighting Championship (UFC) on May 26, 2012 at the MGM Grand Garden Arena in Las Vegas, Nevada. The main card featured five MMA bouts which were shown on PPV, as well as seven preliminary bouts which were shown on FX and Facebook. This was the first time in UFC history that the main card featured all heavyweight bouts. It was the twelfth UFC event of 2012.

The main event featured the UFC Heavyweight Champion, Junior Dos Santos, defending his title against former UFC Heavyweight Champion Frank Mir. The contest was heavily promoted, featuring the return of UFC Primetime to promote the UFC Heavyweight Championship. The co-main event of the evening was a battle between former heavyweight champion Cain Velasquez, and newly acquired Strikeforce heavyweight, Antonio Silva, who made his UFC debut.

Frank Mir was riding a three fight win streak leading up to this event, including a notable submission victory over Antônio Rodrigo Nogueira, a friend and mentor of Junior Dos Santos, at UFC 140. Nogueira refused to tap to the kimura lock submission attempt, until it broke after his arm snapped under the pressure, then he tapped. Not only was Mir the first fighter to ever submit Nogueira, but he did so in devastating fashion. This was the first title defense for Dos Santos since winning the belt by knocking out Cain Velasquez in November of 2011 at UFC on Fox: Velasquez vs. Dos Santos.

The Ultimate Fighting Championship (UFC) is the largest Mixed Martial Arts promotion company in the world, which hosts most of the top-ranked fighters in the sport and produces events worldwide. Based in the United States, the UFC has eight weight divisions and enforces the Unified Rules of Mixed Martial Arts.Dana White serves as the president of the UFC while Frank and Lorenzo Fertitta control the UFC's parent company, Zuffa, LLC.

The first UFC event was held in 1993 in Denver, Colorado. The purpose of the event was to identify the most effective martial art in a real fight between competitors of different fighting disciplines, including Boxing, Brazilian Jiu-Jitsu, Tae Kwon Do, Wrestling, Muay Thai, Karate and other styles. In subsequent competitions, fighters ventured outside their base style to utilize effective techniques from other disciplines, which indirectly helped create an entirely separate style of fighting known as present-day mixed martial arts.

With a cable-television deal and expansion into Canada, Europe, Australia the Middle East,Asia and new markets within the United States, the UFC as of 2011^[update] has gained in popularity, along with greater mainstream-media coverage. As of 2001^[update] viewers can access UFC programming on pay-per-view television in the U.S., Brazil, Australia, Canada, New Zealand and Italy. UFC programming can also be found on FX, Fuel TV, and Fox in the U.S., on ESPN in the United Kingdom and Ireland, as well as in 150 countries and 22 different languages worldwide. UFC also carries a mobile site for on-the-go users and a Sports Bars page for fans to find places showing the pay-per-view. It is also available on the Roku streaming player.

Cain Velasquez Ramirez (born July 28, 1982) is a Mexican American mixed martial artist fighting in the Ultimate Fighting Championship where he is a former UFC Heavyweight Champion. He is a two-time All-American collegiate wrestler from Arizona State University in Tempe, Arizona, and a Junior College National Champ at Iowa Central Community College. He is a two-time 5A state champion in Arizona, compiling a record of 110–10 for Kofa High School in Yuma, Arizona. Cain Velasquez is ranked #2 in the heavyweight division.

Velasquez, a Mexican American, was born on July 28, 1982 in Salinas, California to Efrain and Isabel Velasquez. Velasquez's father, Efrain, came from Mexico to the United States illegally. Efrain met his wife Isabel, married her, and gained US citizenship. Velasquez has two siblings, Efrain, Jr., and Adela. He was raised in Yuma, Arizona. He graduated from Kofa High School, where he compiled a record of 110–10 in four years of wrestling, including winning the 5A Arizona Wrestling Championship twice. Velasquez also played football for three years. As a senior, he served as Captain of both his wrestling and football teams.

Junior dos Santos Almeida (Brazilian Portuguese pronunciation: [ˈʒũnjoʁ dus ˈsɐ̃tus]), also known as Junior Cigano ("Gipsy"; born September 12, 1984), is a Brazilian professional mixed martial artist and the current UFC Heavyweight Champion. He is ranked as the number one heavyweight fighter in the world by numerous media outlets.

Dos Santos started training Brazilian Jiu-Jitsu under Yuri Carlton for fitness reasons. After some time he was invited to join an MMA practice, where he met his boxing coach Luiz Carlos Dórea, and after roughly a year he made his debut fight.

Dos Santos became professional in 2006 at the age of 21. He fought in small promotions in Brazil, such as Demo Fight, Extreme Fighting Championship, Minotauro Fights and Mo Team League. He won 6 out of his first 7 bouts, suffering his only loss to Joaquim Ferreira, a fighter he'd previously beaten.

Dos Santos debuted for the UFC on October 25, 2008 at UFC 90. Considered a major underdog, dos Santos knocked out top contender Fabricio Werdum at a minute and twenty-one seconds of the first round with a strong uppercut, earning himself a "Knockout of the Night" award.

Francisco Santos Miranda, III (born May 24, 1979), better known as Frank Mir, is an American mixed martial artist, as well as a black belt in Brazilian Jiu-Jitsu and Kenpō Karate.

Mir, one of the most accomplished heavyweights in MMA history, is a two time UFC Heavyweight Champion . He currently holds the record for most victories in the heavyweight division of the UFC with 14 and most wins by submission in UFC Heavyweight division history with 8. He is also the only man in UFC history to win a bout by toe hold. As of January 2012 he is ranked the #4 In the ESPN MMA Power Rankings.He holds the distinction of being the first and only man to both knock out and submit MMA legend Antônio Rodrigo Nogueira. Mir is the only person to submit former UFC Heavyweight Champion and NCAA Division I wrestler Brock Lesnar and highly regarded striker Cheick Kongo. Frank Mir has had more fights in the UFC than anyone else currently competing in the heavyweight division.

His father convinced him to begin wrestling, on the basis that it could help him avoid submissions. Mir then began wrestling at Bonanza High School in Las Vegas, Nevada where during his junior year he lost his first nine matches. During his senior year (1998) he went 44–1 and won the state championship. He was also on the school's football team that reached the Southern Zone semifinals in 1997 and where he played as fullback and defensive end. He also took up track and field in 1998 where his discus throw of 177 feet, 10 inches is still a Sunset Regional record.