The famous Nos Galan road races in the south Wales valleys will not take place this year due to coronavirus.
The event attracts about 2,000 runners and 10,000 spectators to the streets of Mountain Ash every New Year's Eve, led by mystery sporting celebrities.
Gatherings of more than 30 people are not currently allowed in Wales due to Covid-19 restrictions.
Organisers said social distancing would be impossible to enforce and have proposed a virtual event instead.
"We have to be mindful that bringing people together from across the south Wales area and much further afield, even if the rules did allow, could cause a significant spike in Covid cases," the organising committee said in a statement.
"While this is a decision we would hope to never have to make, after working so hard to rebuild the event over the last 15 years, cancelling the event on the 31st [of December] is, without doubt, the right thing to do."
A virtual event is being proposed for 2020 where people can register and run on their own, or socially distanced with a small group of friends, according to the Local Democracy Reporting Service.
Inspired by a New Year's Eve race in Brazil, Nos Galan was started by school teacher Bernard Baldwin in 1958 as an amateur race around the block.
It now encompasses races for men, women and children, along with a general fun-run.
The event also celebrates the life of local runner Griffith Morgan - known as Guto Nyth Bran - who died 250 years ago.