"We don't want the Roman summer evenings to be ruined by episodes linked to excessive consumption of alcohol," said mayor Virginia Raggi in a statement.
Similar bans have been put in place in previous years, however this year's is considerably tougher. A total of 14 of the city's 15 municipalities are affected, with the ban in place from 10pm until 7am.
Only the north-western district of Ottavia is exempt from the ruling, while nightlife hotspots including the historic centre, Monti, Trastevere, Testaccio, Prati, and San Lorenzo are all affected.
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From 10pm, it is forbidden to consume alcoholic drinks in glass containers on public streets, while from midnight onwards, the ban extends to any outdoor consumption of alcohol, no matter what the container.
Anyone caught flouting the new regulation could face a fine of €150, while for business-owners selling alcohol after the time limit, that fine increases to €280.
Selling alcohol drinks to take away, for example from off licences or supermarkets, is banned from 10pm onwards, while from 2am, it is also forbidden to serve beverages containing alcohol - even in indoor bars and clubs.
Raggi urged shop owners to print out and display the text of the ban, and urged holidaymakers and locals to continue to "enjoy themselves with a sense of responsibility". The order will remain in place until the end of October.
During the first weekend with the ban in place, over 500 checks were carried out, police said, and 37 fines were issued on Saturday alone.
People eating and drinking in Trastevere's main square. Photo: MoreNovel/Depositphotos
But many businesses and local residents criticized the new rules.
"It limits our freedom as a business, and our free choice as responsible adults to be able to drink after 2am," said the owners of Redrum, a restaurant and bar serving craft beer in the Ostiense neighbourhood. "[It is] a curfew which recalls decidedly sad periods of our history."
Others focused on the fact that Ottavia, the neighbourhood where mayor Raggi lives, was the only district excluded from the ban.
Romans Roberto Di Leo and Elena Cecchini organized a Facebook event inviting people to gather and drink in the area on Saturday evening, with seven public roads and squares as suggested meeting points.
More than 16,000 people said they were interested in taking part, with dozens posting photos of their al fresco drinking on social media.
The new alcohol regulation is one of several temporary bans in place in Rome and across Italy over the summer months, aimed at limiting anti-social behaviour and problems such as littering as the country sees an influx of visitors.
In the capital, authorities have also forbidden eating near, climbing on, or sitting on many of the city's ancient fountains, as well as banning throwing anything into the fountains other than small change which, when tossed into the Trevi, is thought to bring good luck.
And the mayor of the northern city Turin also clamped down on late-night alcohol sales after a stampede at a showing of a football match killed one person and injured over 1,500. It is unclear what caused the moment of panic, but a large number of injuries were cuts due to shards of glass from drinks bottles, many thought to have been bought from illegal sellers.