Switzerland's Roger Federer and Belgian Kim Clijsters were named 2005 world champions by the governing body of tennis (ITF).
World number one Federer is the sixth man to win the award for two consecutive years after Bjorn Borg, John McEnroe, Ivan Lendl, Pete Sampras and Lleyton Hewitt, the ITF said in a statement.
He won 11 titles including Wimbledon and the US Open in 2005.
Clijsters finished the season ranked second behind Lindsay Davenport after a superb comeback from a wrist injury.
She won the US Open, her first grand slam title, after starting the year ranked outside the top 100.