The Royal Welsh Show could take five years to recover from the financial hit of coronavirus, organisers have said.
The estimated cost of cancelling most of this year's event was about £1.2m, John Davies, chairman of Royal Welsh Agricultural Society board said.
There are also fears the future of smaller agricultural shows could be under threat due to the pandemic.
The Welsh Government said a review of agricultural shows had been ordered to look at how best to help.
The Royal Welsh Show, held in Llanelwedd, Powys, draws almost 250,000 people from 40 different countries.
Mr Davies, said: "Our best estimates at this present time tells us our loss to the society, the step back financially for us, is going to be well in excess of £1m, about £1.2m.
"On top of that we've translated it looking at our cash flows, it takes us back at least four to five years."
The Royal Welsh Society also said it was still looking at the possibility of conducting a winter fair.
Across Wales, smaller agricultural shows are also reeling from the financial impact of the virus.
The Anglesey Show is the largest in north Wales, but organisers are also worried about its future.
Show chairman Peter Williams said: "We had the equine flu last year so we had a big financial loss.
"This year we've had to cancel the show and cancel everything that's on in the show fields."
Shows with permanent grounds, such as the Royal Welsh and Anglesey, have lost a considerable amount of income as they are unable to hold other events used to subsidise their main shows.
"It will have a knock-on effect for a while," said Mr Williams.
"If there is a show next year we will have to pare a lot of things down and take it from there and get more local people involved."
The Merioneth County Show is the only show in Wales that still tours from site to site, a saving grace during the pandemic as there are no overheads.
While the financial implications are not as bad as others, there is a fear people will not compete in the future, general secretary Douglas Powell said, such as in the aftermath of the foot-and-mouth outbreak in 2001.
Mr Davies said the Royal Welsh should now receive Welsh Government grants like the Urdd, National and Llangollen eisteddfodau.
"Clearly the support, quite rightly shown, to the National Eisteddfod and the Urdd is welcomed and I hope that the Welsh Government won't find a reason to treat us any differently," he added.
The Welsh Government said it has commissioned an independent resilience review of agricultural shows, looking at how best to help them.