Nearly one in seven youth hostels in England and Wales will shut over the next three years to help fund a revamp of the remaining properties.
The YHA is selling 32 hostels in England and Wales
The Youth Hostels Association said it will sell 32 of its least popular sites and cut around 70 jobs.
It plans to invest £18m in some 200 remaining hostels to upgrade facilities and make them more attractive to visitors.
But countryside groups have expressed their disappointment at the decision.
Jacquetta Fewster, acting co-chief executive of The Ramblers, said: "We are concerned about the impact it will have on walkers."
Tim Bonner, a spokesman for the Countryside Alliance, added: "If this move is restricting access to the countryside for young people and people who are less able to afford alternative accommodation, we would be very disappointed."
But the YHA said it was responding to customer demand for better facilities in more popular locations.
Although overall visitor numbers for the network were healthy, at some sites they were too low to sustain a viable operation, YHA chief executive Roger Clarke told the BBC News website.
"The expectations of young people today are very different from 30 years ago," Mr Clarke said. "People don't like big dormitories and communal washrooms."
He added that the YHA hoped to find alternative sites for nine of the 32 hostels facing closure.
Hostels at the following sites will shut under the new plans: Acomb, Bellingham, Greenhead and Wooler in Northumberland; Alston and Kirkby Stephen in Cumbria; Earby in Lancashire; Keld and Stainforth in North Yorkshire; Langsett near Sheffield; Bakewell and Matlock in Derbyshire; Meerbrook in Staffordshire; Castle Hedingham in Essex; Blackboys, Brighton and Hastings in Sussex; Sandown on the Isle of Wight; Dover in Kent; Ivinghoe in Buckinghamshire; Steps Bridge, Lynton, Dartington and Elmscott in Devon and Quantock in Somerset.
Hostels will shut at the following sites in Wales: Capel-y-Ffin in Monmouthshire; Dolgoch and Tyncornel in Ceredigion; Llangollen in Denbighshire and Trefin in Pembrokeshire.
The hostels facing closure will remain open until at least 31 October.