The year 2012 was the 20th year in the history of the Ultimate Fighting Championship (UFC), a mixed martial arts promotion based in the United States. 2012 started with UFC 142: Aldo vs. Mendes and ended with UFC 155: dos Santos vs. Velasquez 2. The year saw the successful UFC Featherweight title defense by José Aldo, the crowning of Carlos Condit as the Interim Welterweight Champion, a new Lightweight Champion in Benson Henderson, a tournament to crown the first UFC Flyweight Champion as well as the finales of The Ultimate Fighter 15 and The Ultimate Fighter: Brazil.

UFC 142: Aldo vs. Mendes was a mixed martial arts event held by the Ultimate Fighting Championship on January 14, 2012 at the HSBC Arena in Rio de Janeiro, Brazil. It was the first UFC event of the year, and was broadcast live on pay-per-view in North America.