Denmark's Caroline Wozniacki has been crowned International Tennis Federation world champion for 2010, despite not having won a Grand Slam.
The 20-year-old, who unseats 13-time Grand Slam winner Serena Williams as champion, won six tournaments in 2010.
"To be listed with all the former world champions is something I'm really proud of," said world number one Wozniacki.
Rafael Nadal, who won the French and US Opens and Wimbledon this year, regains the men's title from Roger Federer.
Nadal's triumph rounds off a superb year for the 24-year-old.
Having overcome a persistent knee problem, he won the French Open for the fifth time and claimed his second Wimbledon title.
He then became the youngest player ever, and only the seventh in history, to complete a career Grand Slam when he won the US Open in September, in addition to regaining the world number one spot.
Having also won an Olympic gold medal and two Davis Cups, Spaniard Nadal has now won all of tennis's major prizes.
"It is an honour to be named world champion for the second time," he said.
"After a difficult year in 2009, it was an amazing feeling to regain the number one ranking and finally win the US Open.
"My goal all the time is to keep improving and be a better player each year than I was the previous year."
