The race had been held annually since 1897 until it was cancelled this year for the first time, having first been postponed to September from the third Monday in April, or Patriots' Day in Massachusetts, when it usually takes place.
"With fewer than six months until Patriots' Day and with road races prohibited until Phase 4 of the Massachusetts reopening plan, we are unable to host the Boston Marathon this coming April," Tom Grilk, chief executive of the Boston Athletic Association, said in a statement https://www.baa.org/2021-boston-marathon-will-not-take-place-april.
"By shifting our focus to a fall date, we can continue to work with stakeholders to adjust the in-person experience for runners and supporters alike."
The race is regarded as the world's most prestigious marathons and generally draws over 30,000 runners from all over the world.
The BAA will try to announce a new date for the 2021 race by the end of this year.
"We are optimistic that the Boston Marathon will continue its tradition of celebrating the spirit of community and athletic excellence next fall," Grilk added.
"We know there will be many questions and we will look to address them in the coming months ahead." (Reporting by Simon Jennings in Bengaluru, editing by Ed Osmond)