More than 100 people gathered to oppose plans for a new £14bn data centre and battery energy storage scheme in north Devon.
The company behind the project, Xlinks, said the data campus near Great Torrington would be designed to support the local environment and create hundreds of jobs.
Campaigners at the protest at Caddsdown Business Support Centre in Bideford, ahead of a Torridge District Council meeting on Monday, described the proposed AI centre as "absolutely enormous" and a "blot on the landscape".
A government spokesperson said new data centre developments must be considered through the planning system, assessing impacts on communities and the environment.
More news stories for Devon
Listen to the latest news for Devon
Xlinks said in its proposal for the site it would cover about 850 acres (about 345 hectares) but only a third would be developed.
A company spokesperson said the data campus would be designed to support the local environment, while supporting economic growth in the area and bringing 650 to 1,200 permanent high-quality jobs.
They said: "We will ensure that the Devon data campus is designed sensitively, for local people and the environment. Much of the site will be either open to the public or used for planting and to support wildlife by creating new habitats."
Proposals first emerged about an AI data campus, together with associated battery energy storage site (BESS), on farmland between Great Torrington, Huntshaw and Weare Giffard in June.
Campaigners called for a moratorium on planning permissions for data centres but this was rejected by the government on Friday.
In response to whether south-west England needed infrastructure for AI, campaigner Rita Farmer said it was not needed. She had lived in Devon for more than 45 years and described the data centre as "absolutely awful".
She said: "It's just a total blot on the landscape. It's our wildlife. It's everything. None of it washes with me. I'm really angry. All we need is a decent countryside without this blot on the landscape."
Ange Wilson-Duffy said there was a good turnout, showing the "strength of feeling" in the community against the proposals. "We care about it because it's a beautiful, tranquil green space on our doorstep and if this ever went ahead, it takes up so much of that beautiful green space."
Protesters Say Devon Data Centre Would Be ‘Blot on Landscape’