The Amazing Race 21 is the twenty-first season of the American reality competition show The Amazing Race. Hosted by Phil Keoghan, it featured eleven teams of two, each with a pre-existing relationship, competing in a race around the world. This season visited three continents and nine countries and traveled over 25,000 miles (40,000 km). Starting in Pasadena, California, racers traveled through China, Indonesia, Bangladesh, Turkey, Russia, the Netherlands, Spain, and France before finishing in New York City. New twists introduced in this season include the Blind Double U-Turn and the Double Your Money prize. While the prize for winning the season remained at US$1 million, if the team that came in first in the first leg had also won the final leg, the prize would have been doubled to US$2 million. The season premiered on CBS on September 30, 2012, and the two-hour season finale aired on December 9, 2012.

The Amazing Race is an American reality competition show in which teams of two race around the world. Each season is split into legs, with each leg requiring teams to deduce clues, navigate themselves in foreign areas, interact with locals, perform physical and mental challenges, and travel by airplane, boat, taxi, and other public transportation options on a limited budget provided by the show. Teams are progressively eliminated at the end of most legs, while the first team to arrive at the end of the final leg wins the grand prize of US$1 million. As the original version of the Amazing Race franchise, the CBS program has been running since September 5, 2001. Numerous international versions have been developed following the same core structure, while the American version is also broadcast to several other countries.