Britain's undefeated world super-middleweight champion Joe Calzaghe announced his retirement from boxing on Thursday, saying he has nothing left to prove in the ring.

"Deciding to call it a day has been one of the toughest decisions of my life," Calzaghe, whose unbeaten record was 46-0, said on his website.

"There's always the temptation to fight on, especially if you are the champ and no one has ever beaten you. But I've now come to a point where the satisfaction of retiring undefeated has to outweigh the thrill of another fight."

During his 16-year professional career, the 36-year-old Welshman held the WBO, WBA, WBC and IBF super-middleweight belts. He unified the division in November 2007 with a unanimous points win over Denmark's Mikkel Kessler.

Calzaghe then stepped up to light-heavyweight and won a split decision against American Bernard Hopkins in Las Vegas [Images] for the Ring Magazine title in April 2008.

He retained that title after his last fight in November, where he recovered from a first-round knockdown to claim a unanimous decision over American Roy Jones Jr.

GOALS ACHIEVED

Trained throughout his career by his father Enzo, Calzaghe retires as the longest reigning world title holder, having held a world title for nearly 11 years.

"Of course, my special thanks go to my family and, especially to my Dad Enzo who first encouraged me to put on the gloves and who was at my side and in my corner for every one of my fights," said Calzaghe.

"I've also achieved every goal I've ever set myself in the ring -- there are no more mountains left to climb."

Nicknamed the 'Italian Dragon' because of his Welsh mother and Sardinian father, Calzaghe started boxing aged nine and won various schoolboy and amateur titles before turning professional in 1993.

He claimed his first world crown in October 1997 when he beat Chris Eubank for the WBO super-middleweight belt and went on to win 21 consecutive world title fights at that weight.

Calzaghe ends his career three wins short of former world heavyweight champion Rocky Marciano's undefeated record when the American retired from boxing.

The Welshman said he has made many plans for the future.

"I am already working on a number of TV projects and am looking at various commercial offers going forward," he said.

"I shall also be continuing and expanding my charity work which is very close to my heart and, of course, spending a bit more time with the family."