The Barclays ATP World Tour Finals is a tennis tournament played at the end of each year, involving the top eight players in the men's tennis world rankings.

Unlike most of the other events on the men's tour, the ATP World Tour Finals is not a straightforward knock-out tournament. Eight players are divided into two groups of four, and play three round-robin matches each against the other three players in their group. From there, the two players with the best records in each group progress to the semifinals, with the winners meeting in the final to determine the champion. Winners are awarded up to 1500 rankings points.

A similar event on the women's tour is the WTA Tour Championships.

The event is the fourth evolution of a championship which began in 1970. It was originally known as the Masters Grand Prix and was part of the Grand Prix Tennis Circuit. It was organised by the International Lawn Tennis Federation (ILTF) ITF. It ran along side the competing WCT Finals the other season ending championships for the rival World Championship Tennis Tour. The Masters was a year-end showpiece event between the best players on the men's tour, but did not count for any world ranking points.

Roger Federer (German pronunciation: [ˈfeːdəʁɐ]) (born 8 August 1981) is a Swiss professional tennis player who held the ATP No. 1 position for a record 237 consecutive weeks from 2 February 2004 to 18 August 2008. Federer has occupied the #1 ranking for 285 overall weeks, one week short of the record 286 weeks held by Pete Sampras. As of 28 May 2012, he is ranked World No. 3. Federer has won a men's record 16 Grand Slam singles titles. He is one of seven male players to capture the career Grand Slam and one of three (with Andre Agassi and Rafael Nadal) to do so on three different surfaces (clay, grass, and hard courts). He is the only male player in tennis history to have reached the title match of each Grand Slam tournament at least five times and also the final at each of the nine ATP Masters 1000 Tournaments. Many sports analysts, tennis critics, and former and current players consider Federer to be the greatest tennis player of all time.

Federer has appeared in an unprecedented 23 career Grand Slam tournament finals, including a men's record ten in a row, and appeared in 18 of 19 finals from the 2005 Wimbledon Championships through the 2010 Australian Open, the lone exception being the 2008 Australian Open. He holds the record of reaching the semifinals or better of 23 consecutive Grand Slam tournaments over five and a half years, from the 2004 Wimbledon Championships through the 2010 Australian Open. At the 2012 Australian Open, he reached a record 31st consecutive Grand Slam quarterfinal. During the course of his run at the 2012 French Open in Roland Garros, Federer eclipsed Jimmy Connors long standing record of 233 match wins in Grand Slam tournaments when he defeated Adrian Ungur in a second round match.

Rafael "Rafa" Nadal Parera (Catalan: [rəˈfɛɫ nəˈðaɫ pəˈɾeɾə]; Spanish: [rafaˈel naˈðal paˈɾeɾa]) (born 3 June 1986) is a Spanish professional tennis player and a former World No. 1. As of 28 May 2012 (2012 -05-28)^[update], he is ranked No. 2 by the Association of Tennis Professionals (ATP). He is widely regarded as one of the greatest players of all time; his success on clay has earned him the nickname "The King of Clay", and has prompted many experts to regard him as the greatest clay court player of all time.

Nadal has won ten Grand Slam singles titles, including a record six French Open titles (tied with Bjorn Borg), the 2008 Olympic gold medal in singles, a record 21 ATP World Tour Masters 1000 tournaments, and also was part of the Spain Davis Cup team that won the finals in 2004, 2008, 2009 and 2011. He completed the Career Grand Slam by winning the 2010 US Open, being the seventh player in history, and the youngest in the open era, to achieve it. He is the second male player to complete the Career Golden Slam (winner of the four grand slams and the Olympic Gold medal) after only Andre Agassi.

David Pablo Nalbandian (born January 1, 1982) is an Argentine professional tennis player and former world no. 3. He was runner-up at the 2002 Wimbledon Championships and the winner of the Tennis Masters Cup in 2005.

David Nalbandian was born in the small city of Unquillo in Córdoba Province, Argentina. His mother is of Italian descent and his father is of Armenian descent. He turned a professional tennis player at the age of 18.

He turned professional in 2000. In 2001, he finished in the ATP top 50 for the first time. He finished 2002 as the no. 1 Argentine and South American for the first time in his career, winning two ATP titles and reaching the Wimbledon final, where he lost to Lleyton Hewitt.

Nalbanian was not able to return to the Wimbledon final in 2003, as he was knocked out in the round of 16 by hometown favourite Tim Henman. He did however make an impressive run at the U.S. Open, taking out both of the Wimbledon finalists 20th seed Mark Philippoussis, and the second seed Roger Federer along the way to a semifinal matchup with Andy Roddick. It was the second time in less than a month that he had met Roddick in a high-stakes match, having lost to him in the final of the Rogers Cup a few weeks earlier. Nalbandian started strongly, taking a two sets to love lead, and held a match point in the third-set tiebreak. There was a little bit of controversy during the match, when a fan yelled "out" at 7–7 in the tiebreak, causing Nalbandian to mishit his following shot when he thought the linesman was the one who called it. Roddick took the point and eventually prevailed in the tiebreak. Ultimately, he was unable to finish the match off and eventually lost 6–7, 3–6, 7–6, 6–1, 6–3. He finished 2003 ranked #8 in the world.

David Ferrer Ern (Valencian pronunciation: [daˈvit feˈreɾ ˈɛɾn]; born April 2, 1982 in Xàbia, Marina Alta, Valencian Community) is a Spanish professional tennis player who lives in Valencia, Spain who is currently World No. 5 in the ATP Rankings and is the second-highest ranked Spaniard behind World No. 2 Rafael Nadal. He turned professional in 2000. Ferrer is known as a clay-court specialist, although he has had success on hard courts as well, as evidenced by his semifinal appearances at the 2007 US Open and 2011 Australian Open. He was part of the Spain Davis Cup team that won the finals in 2008, 2009 and 2011. He was also runner-up at the Tennis Masters Cup in 2007. He first achieved a top–10 ranking in 2006 and reached a career high ranking of no. 4.

Ferrer was born in Xàbia in the province of Alicante, but he moved to Gandia at age 13, followed two years later by a move to Barcelona to attend the Catalan Tennis Federation. He spent nine months at Equelite, Juan Carlos Ferrero's Academy in Villena, before moving back to Xàbia while practicing in Denia.