As director of the Institute of Nephrology in Cardiff for 17 years, the professor was head of one of the world's leading centres for research into kidney disease.
But for the last five years he has also been Wales rugby team doctor, playing a pivotal role in the creation of the all-conquering super-fit Six Nations squad of last season.
The Llanelli-born professor, 57, received his award from Wales coach Mike Ruddock at a night of celebration and fundraising for the Kidney Wales charity.
Professor Williams, who lives in Cathedral Road, Cardiff, told the 300 guests at the Kidney Wales Walk for Life Celebration Dinner at Cardiff City Hall: "Life's all about being lucky.
"I've been lucky in many ways, in having such a good staff at the institute and the backing of such a supportive charity which has helped make it the greatest research centre for kidney disease in the world.
"And I've certainly been fortunate in being a part of the Welsh rugby squad this year."
Ruddock, who described the professor as a vital part of the Grand Slam winning squad, said: "Our rugby stars have never been fitter or healthier, and that played a major part in our success this season."
The Institute of Nephrology - which started life at Cardiff Royal Infirmary before moving to the University Hospital - has been at the forefront of the detection, prevention and treatment of kidney disease in Wales.
And Professor Williams' award marked the unique work of his team at the research centre into dialysis and transplant techniques which has given tens of thousands of kidney patients a new life.
Professor Williams, who has also been part of the medical team at the Cardiff Blues Rugby Club since 1996, will be travelling with the Wales squad next month on their tour to North America.
Earlier in his career he was the doctor on a racing yacht in the Indian Ocean, a medical mountaineer on two Himalayan expeditions - and a family GP.
Kidney Wales chairman Roy Thomas said: "Professor Williams has a global reputation and has promoted the importance of research into renal failure.
"His leadership is one of the main reasons this charity supports the Institute of Nephrology and he deserves our Lifetime Achievement Award for his dedication and energy."