Land next to the Grapes Pool off Moseley Road, Bilston, Wolverhampton, represents one of very few green spaces left in the Bilston North council ward.
But councillors say the site has been earmarked for development as part of the Black Country Plan, which puts forward land which could be built on in the coming years to meet the region's housing need.
They have vowed to fight any proposals to develop the site in a bid to save the fields for future generations in Bilston.
It is understood that 85 homes have been earmarked for the site under plans which are due to be officially released today.
Councillors' Phil Page, Olivia Birch and Linda Leach, who all represent Bilston North, are opposing the plans.
Councillor Leach, whose Save Grapes Pool Field group on Facebook has nearly 800 members, said: "We understand that homes have got to be built because there is a need for housing, but we are running out of green spaces and we need to protect them.
"The green field at the back of the Grapes pool is beautiful. People use it for exercise and they have picnics there in the summer. A mini-forest is being built there at the moment.
"There's a man who has been in touch with us who has got his wife's ashes scattered over there.
"During the Covid lockdowns when people couldn't travel the space was used a lot so people could get out. It is important for people's mental health, and where else are they going to go?
"It's a personal thing – not just for people who live near there but for people who have moved away as well.
"I understand that we haven't got enough brownfield sites and that means that some green land has to go, but we will be doing all we can to make sure this site is protected."
Councillor Page said: "From the response we have had in Bilston North, it is clear there is universal opposition to the proposal to build 85 houses on the field.
"It is the last truly open space in the ward, as the one at Prouds Lane is a lot smaller and is surrounded by fences."
The Black Country Plan is due to be released today, having been put together by the area's four local councils to replace the Black Country Core Strategy.
It will be voted on by councillors ahead of a full public consultation, which is expected to start in August.
The plan has already sparked controversy after Wolverhampton councillor Paul Birch revealed the Seven Cornfields was not included, meaning no development would take place on the sprawling site between Penn and Sedgley.
His actions were described as "irresponsible and dangerous" by Dudley Council's cabinet member for regeneration, Councillor Simon Phipps, who said Councillor Birch may have jeopardised plans to save the green belt.