The Cardiff Half Marathon scheduled for October 4 has been postponed until 2021 due to the coronavirus
Organizer Run 4 Wales says holding it in just four months' time "really isn't feasible" and the event will instead take place on 28 March next year.
Since its foundation in 2003, the event has become the UK's third biggest race after the London Marathon and the Great North Run.
Last year 27,500 runners and 100,000 spectators attended the race.
The 2019 Cardiff Half Marathon saw men's winner Leonard Langat from Kenya finish the 13.1 mile course in a new record time of 59 minutes 29 seconds.
"There's still uncertainty about what the autumn looks like," Run 4 Wales chief executive Matt Newman told BBC Sport Wales.
"The prognosis is not very good at the moment and it looks like [mass] events are going to be one of the last things to come back when the world starts to settle down.
"Whilst we could have left this for 12 months and come back in the autumn of 2021, we wanted to give participants an option to come in March which we feel is long enough away for the world to start to come back to some sort of normality."
The Cardiff Half had been due to take place on the same day as the rearranged London Marathon. As it stands that event is still due to go ahead.
The Newport Wales Marathon - already postponed from April to October - has been pushed back again to a new date of 18 April 2021.
Newman is hopeful that postponing the Cardiff Half will allow organisers to hold an event "virtually as normal" next spring, but admits Run 4 Wales is preparing for some restrictions to still be in place.
"We're getting lots of information about how the running community across Europe is looking to stage events," he said.
"There's a lot of creativity going on about different waves, different start times, putting in place all sorts of safe practices.
"But right now it's a little bit early to explain all the options, as we're still hopeful that by the spring of 2021 some of the restrictions we have at the moment are relaxed."
The Cardiff Half Marathon typically sees more than £4m raised for charities and the hope is that only delaying the event will mean these good causes will not miss out on vital fundraising.
Next year will see two half marathons take place in the Welsh capital, with the autumn event still scheduled for 3 October 2021.
posted Thursday June 4th
by Tom Brown