Around 12 caravans have been set up in Lincoln near the Grandstand on the West Common.
Officers at the City of Lincoln Council said they are working to evict the travellers as soon as possible.
The council said in a statement on social media : “We are aware that an unauthorised traveller encampment has set up overnight outside the Grandstand on the West Common.
“In response, we have enacted our protocol for such incidents and are working with our partners to begin their removal, following the usual legal process.
“We will ensure full compliance with our legal duties but will, of course, also ensure that these are completed in the fastest time possible.
“We ask residents and visitors to the common and the Grandstand to be patient while this matter is resolved.”