Will Skelton has extended his contract with the Waratahs and the ARU for two more years through to 2017.
The giant second row has established himself with the Wallabies since making his debut in 2014, showing improved fitness this season for the 'Tahs.
Skelton explained that he had put in a lot of work to become a more complete player, and feels he still has a big margin for improvement.
"I've been blessed to have had an opportunity to play for the Wallabies and to win a Super Rugby title, but I still feel I have a lot of improvement left in my game," Skelton said.
"You need to have high standards for yourself and I've been working extremely hard throughout the year to work on all areas of my game to make me a complete 80-minute player."
He will work under new Waratahs coach Daryl Gibson, who has stepped up from assistant after Michael Cheika's permanent move to the Wallabies.
"Will is the type of player that you can build a team around, he's got a huge presence on the field physically and is one of the most skilful players I have coached over the years," Gibson said.
"He had another excellent season in 2015, and is undoubtedly one of the highest performing forwards in Australian rugby, he's growing into an outstanding player and leader within the club."