Right-back Darby who joined Wanderers in the summer of 2017, received the diagnosis from a specialist recently.
“It is with great sadness that I announce my immediate retirement from professional football due to a recent diagnosis of Motor Neurone Disease,” he said in a statement released by the Championship club.
“I would like to take the opportunity to thank my team-mates, (manager) Phil Parkinson and all the staff at Bolton Wanderers Football Club for their amazing support at what has been an extremely difficult period for myself and my family.
“I would like to ask for privacy at this time so I can adjust to the battle I have ahead and so that I can spend time with those closest to me.”
Bolton boss Phil Parkinson added: “This is heart breaking news for Stephen and his family and the thoughts of everybody at Bolton Wanderers Football Club are very much with him and Steph.
“He is an outstanding professional and a fantastic person.
“He was simply magnificent during his time at Bradford and was a key figure in the resurgence of Bradford City as a football club.
“He typified everything the city and the football club represented and led by example on and off the pitch.
“The Bolton Wanderers fans didn’t see the best of him due to limited first team opportunities, but I can assure everyone that he made a significant contribution in last year’s survival.
“He constantly set high standards in training every day and encouraged and drove his fellow teammates on.
“All the staff and players at Bolton Wanderers Football Club think the world of him and are determined to give him every possible bit of support.”
Fans were quick to take to Twitter with messages of support for the 29-year-old in the wake of his heartbreaking diagnosis.
“Horrible news and absolutely gutted for Stephen,” one fan wrote. “Met him through a supporters event and he’s a lovely guy. You’ll never be short of support, whether it’s Bolton, Bradford or Liverpool.”
Another supporter said: “Thoughts with him and his family. Devastating news.”
“Wow. I cannot believe this. Only 29 years of age. Stay strong Stephen,” a third fan wrote.
Bradford City tweeted a message of support for their former captain.
“We will be offering full support to former @officialbantams star Stephen Darby, who today announced his retirement from professional football after being diagnosed with motor neurone disease,”
Swindon Town – whom Darby spent a brief loan spell at back in 2010 and where he scored the decisive penalty in the shoot-out against Charlton Athletic in the play-off semi-final – also offered their supporter to the defender.
They wrote: “Everyone at #STFC is devastated to hear of Stephen Darby’s diagnosis with Motor Neurone Disease.
“Along with the rest of the #FootballFamily, we send our best wishes to Stephen and his family.
“He provided us with one very special moment in particular.”