Some of these athletes are right in their primes, some have a long track record of sustained success, and some are athletes just beginning their dominance.
We recently ranked the most dominant athletes in sports in general, but we also chose the most dominant in each sport individually.
From the NFL and NBA to soccer, tennis, golf, track and field, and more, we selected the 31 athletes who stake a claim as the best in the world at what they do.
Real Madrid forward
Ronaldo took home the Ballon D'or in 2014 and carried Portugal to the World Cup despite being knocked out in the first round. He has 18 goals in 2015 and 50 goals in 47 games for the 2014-15 season.
German national team midfielder
Kessler won 2014 FIFA's women's player of the year and leads a German team that's one of the favourites going into the 2015 Women's World Cup.
Serbian tennis player
Djokovic is the No. 1 ranked tennis player in the world, and seems best poised to dominate in the near future. He's the first player to win the year's first three Masters 1000 tournaments -- the biggest outside the Grand Slams -- and has a 5,000-point lead over Roger Federer for the No. 1 rank.
American tennis player
Williams won seven titles in 2014, including the US Open, and is 20-0 in the 2015 season. Her own inconsistency is her biggest problem, but when she's healthy and focused, she's unbeatable.
Cleveland Cavaliers forward
LeBron James has a rightful case for MVP each season. The Cavaliers won 20 more games with James this year while the Miami Heat lost 17 more games without him. All the while he puts up monster stats every night.
Minnesota Lynx guard
Moore won the 2014 MVP award, averaging 24 points and 8 rebounds per game, and then led USA Women's Basketball to gold in the 2014 FIBA World Cup while winning player of the tournament.
Houston Texans defensive end
Watt is the reigning NFL defensive player of the year and the runner-up for MVP. He had 20.5 sacks on the year, one interception, and even had three receiving touchdowns on offence. He's almost uncontainable for offensive lines.
Bolt doesn't compete often outside of the Olympics, but when he does, he dominates. He set the world records for 100m and 200m at the 2012 Olympics. He recently ran his slowest 100m time ever, and still won the race.
Ethiopian middle- and long-distance runner
Dibaba was named 2014 sportswoman of the year for setting indoor world records for 1500m, 3000m, and a two-mile. She ran the second-fastest 5K ever in March, missing the world record by two seconds.
Hirschel has been the men's No. 1 ranked skier for four years. He's the first skier to win four straight World Cup titles, and he needs just two more to have the most titles overall.
Maze took home three medals at the 2015 World Ski Championships, including a gold medal in the combined event -- an event that's 'designed to determine the best all-around skier.' She was nominated for Laureus Sportswoman of the Year in 2015.
Jones has a 21-1 record in the UFC and has won his last three fights by unanimous decision. Off-field issues continue to plague him though; he tested positive for cocaine, and was stripped of his UFC title after getting arrested in connection with a hit-and-run accident.
Rousey typifies dominance. She's 11-0 in MMA and 5-0 UFC fights. Her last two fights have lasted an average of 15 seconds.
South African swimmer
Le Clos was named FINA World Swimmer of the Year in 2014 after he dominated the 2014 World Championships, winning gold in the 50m, 100m, and 200m butterfly, as well as the 200m freestyle. He also won two gold medals in the 2014 Commonwealth Games, one for the 400m medley.
Ledecky is a three-time All-Met Girl's Swimmer of the Year and currently owns the world records in the 400m, 800m, and 1500m freestyle. She could become the first woman to win four individual gold medals at a single World Championship this August.
Los Angeles Dodgers pitcher
Kershaw had one of the best pitching seasons in MLB history on his way to winning the 2014 Cy Young. He led MLB in wins, ERA, WHIP, and was second in opposing batting average.
Starc helped lead Australia to win the 2015 World Cup and was named Player of the Tournament in the process. He led the entire tournament with 22 wickets.
Taylor was the T20I Women's Cricketer of the Year in 2013, and during a stint playing in Australia in 2014 was named the South Australian Scorpions Player of the Year for 2014-2015.
Ovechkin was first in goals in 2014-15, scoring 53 -- his most since 2009 -- and had 81 points, the fourth-best in the NHL and his most since 2010.
Egyptian squash player
Elshorbagy is the No. 1 ranked squash player in the world. He won five events in 2014, including the World Series tournaments in Hong Kong and the US Open.
Malaysian squash player
David has been the world's No. 1 ranked women's squash player for eight years running and is often considered the greatest women's squash player ever. In 2014, she won a record-setting third straight US Open title.
McIlroy didn't win The Masters as he was expected to, but he did finish in fourth place with -12, his best finish ever. He needs one Masters win to become the sixth player to ever accomplish a career grand slam.
New Zealand golfer
Ko became the youngest No. 1 ranked player in professional golf in 2015. In 2014 she won three LPGA tournaments and has already won the Women's Australian Open in 2015.
Norwegian road cyclist
Kristoff has steadily improved since becoming pro in 2010. He had 14 victories in 2014, including two stage victories in the Tour de France, and he has 11 victories already in 2015.
Japanese figure skater
In 2014 Hanyu took first place for the second straight time at the Japanese Figure Skating Championships, won a gold medal at the 2014 Olympics, and won the 2014 World Championships in Japan. In 2015 he's already won his third straight national Japanese title and recovered from an injury to finish second at the World Figure Skating Championships.
Russian figure skater
After a poor showing at the 2014 Olympics, Tuktamysheva has already won the Grand Prix Final, the 2015 European Championships, and dominated the 2015 World Championships, winning by nearly 17 points.
British Formula 1 driver
Hamilton won his second season title in 2014, and already has three first-place finishes and a second-place finish in 2015.
Uchimura is often considered the greatest gymnast of all time. He's won five Olympics medals and 16 World medals. In 2014 he became the first gymnast to win five consecutive World all-around titles.
Biles is set to dominate her first Olympics in 2016. She won four gold medals at the 2014 World Championships and took first place at the 2015 AT&T American Cup.
New Zealand rugby player
McCaw is the captain of the All Blacks, New Zealand's national rugby team, which won the 2011 World Cup and the 2014 World Rugby Team of the Year. McCaw has won World Rugby Player of the Year three times and has been nominated five other times.
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