Around two dozen caravans set up camp in Catcliffe over the weekend.
It is reported that they are using the changing rooms, toilets and showers normally used by local football teams.
They have parked their caravans, vans and cars on football fields on the community land, which backs onto a number of gardens.
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The illegal traveller site is opposite the new Waverley housing development and close to Morrisons supermarket.
In a Facebook post, Catcliffe Parish Council said: “We're aware of the travellers’ invasion on the Recreation Ground.
“We have no powers to evict them. We're continuing to look into what we can and can't do, which will probably mean a court order eventually.
“Many thanks to everyone who has been in touch or rang the police.”
To report incidents relating to the site to South Yorkshire Police, call 101 and quote incident 861-190621.