Novak Djokovic, Serena Williams ITF world champions

Serena Williams and Novak Djokovic have been named the International Tennis Federation’s world champions after dominating in 2015.

The duo have been in sensational form over the last 12 months, winning three grand slams apiece and only losing nine matches between them on tour.

Williams – who finished the year 50-3 – ploughed through the competition in the opening three major tournaments of the year, claiming her sixth Australian Open, a third French Open and sixth Wimbledon crown.

She missed out on a calendar Grand Slam at the US Open, though, as she was beaten by Roberta Vinci in the semi-finals.

“It means a lot to me to be named the ITF World Champion for the sixth time,” she said. “I am proud to have achieved my second Serena Slam, in what has been an amazing year for me.”

Meanwhile, Djokovic was also triumphant in Melbourne before finishing the year with titles at Wimbledon and Flushing Meadows – beating long-time rival Roger Federer in the final.

The Serb added the ATP World Tour Finals crown to his achievements in 2015, earning him a fifth successive world champion award.

Djokovic said: “It is an honour to be named ITF World Champion for the fifth time. My season was the best of my career with many highlights.

“It inspires me even more to keep on going, and I hope to continue to play at this level in 2016.”