The object, which is 14cm (5.5in) long, was found during an excavation for a new housing development in Brunswick Road, in an area that would have been just behind the city's Roman wall.
Experts say it was probably part of a winged statuette to Victoria, the Roman goddess of victory.
It will be put on display at Gloucester Museum once it has been studied.
Neil Holbrook, from Cotswold Archaeology, said: "This find once again demonstrates that Gloucester was a high ranking city in Roman Britain and that its public spaces must have been equipped with a number of bronze statues of gods and emperors."
He added that finds of Roman bronze sculpture in Britain are "extremely rare" and "very few depictions of Victoria or eagles" are known from the province.
"It would be nice to think a retired Roman soldier, spending his retirement years in Gloucester, had a nice statuette to Victory as thanks for making it through the Roman invasion of Britain in one piece."
Initially, archaeologists said they believed the wing came from a statue of an eagle, but Dr Martin Henig, an expert on Roman sculpture at Oxford University, studied the object and believes it is likely to have come from a statuette to victory.
An "extremely rare" Roman bronze wing has been found during an archaeological dig in Gloucester.