People hurled chairs and tables at each other during a brawl at the Mailroom Cocktail & Wine Bar.
There “was not a table that was not fighting”, according to one witness.
The chaos is said to have spilt out into the street with onlookers fleeing the area fearing for their own safety.
The fight was reportedly sparked after a woman pushed a girl at another table at around 7.30pm.
Things “escalated” with between 20 and 30 people becoming embroiled in the ruckus.
However, no one was arrested and no complaints were made, according to police.
A police spokesperson added: “We were called at 7.30pm on Saturday 12 September to a report of a group of people fighting in Oxford Street, Southampton.
“Officers arrived. No complaints were made and no injuries reported. No arrests have been made.”
Anyone with information is urged to call police on 101 quoting 44200353378.
The Daily Echo has contacted the Mailroom for comment.