Two people were arrested and 38 others fined after police thwarted an unlicensed music event in Fishponds.
Officers spotted a 'Bristol Freerave' being promoted for a secret location on social media on Saturday night (9 January).
A 19-year-old man was arrested before the event was due to start, and has since been released under investigation
Officers from Avon and Somerset Police went to Oldbury Court in Fishponds where a significant number of people started to arrive around 8.30pm.
Police issued 38 fixed penalty notices for breaching Covid regulations and around 30 under 18's were spoken to.
A second arrest was made in connection with a drink driving offence, and a vehicle was seized for having no insurance.
Police stayed at Oldbury Court until the early hours to make sure no event could take place.
Patrols were also held around Eastville Park and Lodge Causeway but no unauthorised gatherings took place.
Chief Inspector Paul Wigginton thanked those who alerted the force to the planned rave, and said the key to preventing these events from happening is to stop them before they get underway.
He said, "An abnormally large number of vehicles and/or people arriving in an unusual area, or loud speakers being unloaded are the sort of red flags that could suggest an unauthorised music event is due to take place.
"We urge anyone who spots the signs of an event being set up to get in touch with us immediately on 101."