The former Scotland international, who won 61 caps, used his profile to push for better research to be carried out into MND and appealed for improved care to be given to those afflicted by it.
Weir’s wife Kathy announced his passing through the SRU in a statement tweeted this evening.
"It is with great sadness that we announce the death of our beloved husband and father, Doddie.
"Doddie was an inspirational force of nature. His unending energy and drive, and his strength of character powered him through his rugby and business careers and, we believe, enabled him to fight the effects of MND (Motor Neurone Disease) for so many years.
"Doddie put the same same energy and even mor elove and fun into our lives together; he was a true family man. Whether working together on the farm, on holiday, or celebrating occasions with wider family and friends, Doddie was always in the thick of it. We are lucky to have shared our lives with him and we cherish all those memories: his love and warmth, his support and advice, his quick wit, and his terrible jokes. It is difficult to put into words how much we will miss him.
"MND took so much from Doddie, but never his spirit and determination. He battled MND so bravely, and whilst his own battle may be over, his fight continues through his foundation, until a cure is found for all those with this devastating disease.
"Hamish, Angus, Ben and I would like to thanks everyone for your support and for respecting our privacy at this difficult time.”
First Minister Nicola Sturgeon tweeted: “This is so terribly sad. Doddie was one of our nation’s sporting legends, but the brave way he responded to MND surpassed anything ever achieved on the rugby pitch. He refused to let it dim his spirit and did so much to help others. My condolences to his loved ones. #RIPDoddie”.
Jill Douglas, chief executive of My Name’5 Doddie Foundation and a close friend of Weir’s, said: “Doddie enjoyed a full life full of fun and love. And it was this approach to life which shone through in his determination to make a difference and help others when he was diagnosed with motor neurone disease.
“He inspired us every day with his positivity and energy and was fully committed to the work of the foundation he launched with his close friends in November 2017. My Name’5 Doddie Foundation continues to shine a light on MND and the need to seek meaningful treatments and, one day, a cure for this devastating disease.
“The foundation has raised significant funds through the amazing efforts of our incredible supporters and has committed £8 million to MND research over this time. We have also given considerable funds to people living with MND and their families to help them live as fulfilled a life as possible.
“With Doddie’s enthusiasm and drive, we have collaborated with other stakeholders within the MND community and firmly established the foundation as a trusted, influential and well supported charity.
“And our vision of a world free of MND remains at the heart of our strategy. As we look to the future, we will honour Doddie’s name and deliver on his legacy.
“There is much still to do and with your support, we will continue our work, remaining true to the values and ambition of our founder.”
Former club Newcastle said in a statement: “It is with desperate sadness that Newcastle Falcons has learned of the passing of our former player and lifetime friend, Doddie Weir OBE.
“A legend as a player, Doddie helped the Falcons ascend into the top flight and was an instrumental part of the squad which lifted the 1997-98 Premiership title – still the only team to achieve this remarkable feat the first season after promotion.
“Following his diagnosis of motor neurone disease in 2017 Doddie showed his characteristic mixture of determination and good humour in raising many millions for research into the currently-incurable condition.
“It was our honour to display his foundation’s logo on the front of our shirts when we played at St James’ Park in front of a club record crowd of more than 30,000 in 2018, and to play our part in supporting their incredible fundraising activity.
“All associated with Newcastle Falcons would like to express our sadness at hearing the news of Doddie’s passing, whilst at the same time remembering the many happy memories and good times of which he was a central part.”
Wales head coach Wayne Pivac began his post-match press conference following a 39-34 Autumn Nations Series defeat against Australia in Cardiff by paying tribute to Weir.
“On behalf of the Welsh rugby public and the Welsh national team, we would like to send our condolences to Doddie’s family,” Pivac said.
“A terrific man, I was fortunate enough to meet him after a Scotland-Wales game.
“He has done a lot for the game, and our condolences go out to his family and friends.”