A decision taken by Belfast City Council means children under the age of 15 will be able to watch the new Batman film if they are accompanied by an adult.
The Batman had originally been given a 15 rating by the British Board of Film Classification (BBFC).
Belfast is the only location in the UK where the movie, starring Robert Pattinson, will have a 15A rating.
That is a certification more often used in the Republic of Ireland.
The BBFC describes the film, which is released on Friday, as "a crime thriller in which a vigilante teams up with a detective to solve a series of murders perpetrated by a riddle-loving killer".
On its website, the body says the film exceeds the guidelines at 12A, but was suitable for audiences aged 15 and over.
While the BBFC classification is a guideline for cinemas, their licences to exhibit films are granted by local councils and authorities, which means councillors have the final say on what can be shown on the big screen, and who can see it.
In February, a proposal to re-classify The Batman as 15A was brought to Belfast City Council's (BCC) Licensing Committee by a local cinema chain, but was narrowly defeated.
The issue was then brought to a full council meeting earlier this week by Sinn Féin councillor Arder Carson.
Mr Carson told the meeting: "My Batphone has been ringing off the hook for these last two weeks with people asking me what in the sweet name of Gotham City is going on in that licensing committee.
"Given what is going on in the world and the last two years of lockdowns and restrictions, this seems like a small potato to us, yet it is such a big deal to hundreds, if not thousands, of young people.
"I think we need to trust our parents."
The motion to rate the film as a 15A in Belfast cinemas was then agreed upon without a vote.
Dr Sian Barber, a senior lecturer in British Cinema, Film and History at Queen's University Belfast, described the decision by BCC as "fascinating and quite progressive".
But she added: "It's a really slippery slope. Once you start doing it, where do you stop?"
Dr Barber said the hype around The Batman means it is a film that could get people back to the cinema after two years of the Covid-19 pandemic and will therefore make a lot of money.
"So why not actually extend it and make sure you can get as many bums on seats as possible?," she said.
The Batman is not the first superhero movie to have its classification relaxed.
The 2002 film Spider-Man had its 12 certificate downgraded to PG by councillors in parts of England amid public pressure, but a number of other authorities decided to stick to the BBFC's recommended classification.
What about the rest of the UK?
The BBFC says it has no current plans to introduce a 15A rating for other UK audiences as there has been little public feedback from parents in favour of it.
It said: "The content of films with a 15 age rating is stronger in terms of discriminatory language and behaviour, drug taking, sex and violence, and these are all elements that parents tell us are not acceptable for children aged around 12."
The Batman franchise has caused issues for the BBFC in the past.
The decision to rate Christopher Nolan's 2008 film The Dark Knight as 12A generated 364 complaints, which the body says was by far the largest number it has ever received about a single film.
Many of those complaints said the film was too dark and violent for children.
When it comes to the latest offering in the Batman universe, Dr Barber says there will be younger teens who will want to see it, and there will be other teens who will "be scared out of their wits".
"It's a really tricky one, but I do think other local councils and local authorities are going to come under pressure to take another look at this film", she added.
Like most good movies, Dr Barber believes there will be a a sequel to the BCC decision.
But it may well be in the form of a backlash.