More than 20 caravans arrived at the park in Heaton Place on Sunday afternoon (July 25).
After setting up a makeshift camp, the travellers were asked to vacate the site by officers from Preston City Council.
Councillor Robert Boswell, Cabinet Member for Environment and Community Safety at Preston City Council, said: "We are aware that a group of Travellers have set up camp on Ribbleton Park having gained access via Blackpool Road.
"Officers from the council have visited the site to make contact with the group and we have commenced the process to remove the group from the site.
"Any waste left behind will be cleared when they have moved on."
It is not clear how long the group have been given to vacate the site, but aerial pictures show several caravans remained on the site yesterday (July 29).
Preston City Council has been approached for an updated comment.
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