Federer and Williams enjoyed a successful 2009
Roger Federer and Serena Williams have been named as 2009's world champions by the International Tennis Federation after topping the year-end rankings.
Federer, who wins the honour for the fifth time, completed a career Grand Slam at Roland Garros before winning his 15th Grand Slam title at Wimbledon.
And Williams won the Australian Open and Wimbledon, her 11th major success.
The pair will receive their awards at the annual ITF world champions dinner in Paris in June.
Federer regained the world number one ranking from Rafael Nadal after his Paris victory and his Wimbledon win over Andy Roddick saw him surpass Pete Sampras' haul of Grand Slam titles.
He was also runner-up at the Australian Open and the US Open and helped his country retain its Davis Cup world group status.
"It is an honour for me to be named ITF world champion for a fifth time. It was an incredible year for me both on and off the court," said the 28-year-old Swiss star whose wife Mirka gave birth to twin girls in July.
"To win my first Roland Garros title, break the all-time Grand Slam record and regain the number one ranking is amazing. It means a lot to me to finish the year again at the top."
Williams takes the award for the first time since 2002. As well as her Grand Slam wins, she won the season-ending WTA Championships in Doha, sealing the top ranking in the last event of the year.
She also took the doubles year award with sister Venus after taking their career total to 10 Grand Slam titles. In doing so she joins Lindsay Davenport and Martina Hingis as the only players to become singles and doubles world champions in the same year.
American twins Bob and Mike Bryan were named as the men's doubles world champions for the sixth time in seven years.