The first ever "Girl Summit" is being held in the UK, aimed at increasing efforts to end female genital mutilation (FGM) and child, early and forced marriage (CEFM) within a generation.
Co-hosted by UNICEF and the UK Government the event is being held in London and brings together government representatives, international organisations, the private sector and girls themselves to call for action.
Organisations involved say millions of girls and women are being prevented from achieving their potential, or live a life free from violence, because of harmful practices such as FGM and CEFM, which are illegal in the UK.
Sky News spoke to one Kurdish woman who, at the age of 15, was forced to marry a man she didn't know, and was subsequently beaten and raped.
Speaking through a translator, she described how her own relatives attacked her when she tried to escape.
"Her own family tried to kill her for leaving her husband," the translator said.
"They stabbed her twice, once in the chest and another in the back, and this was done by her brothers.
"When she did escape she was also prevented from seeing her children for 15 years. This has had a tremendous psychological effect."
But Diane Nammi from the Iranian and Kurdish women's rights organisation says this isn't just a distant problem.
"It happens in London, in Newcastle, anywhere in the UK," she said.
"They are doing it mainly where there is sharia law and sharia courts, and so many young girls can be wife of a man as old as their father or grandfather, they can be the second wife of a man."
It's estimated that 14 million girls are married every year before they reach 18, with one in nine across the developing world married by 15.
Some 60% of child brides are also taken out of school so they have no formal education.
In most countries the legal minimum age for marriage is 18 - but loopholes often allow it to happen as part of local customs.
The group Girls Not Brides told Sky News that change is happening within communities and families in the UK, and across Africa, South Asia, the Middle East and Europe, with more and more saying no to this form of abuse.
But Heather Hamilton from the partnership said many still don't realise the harm child marriage causes.
She said: "It's an entire end to the girl's life as her own person.
"We take it for granted that we’re going to be able to make choices and have opportunities.
"We're going to be able to choose whether we get married, go to school or university.
"It's almost inconceivable for women who have the privileges we have to understand what this means, but it has a devastating impact on the girls and their lives."
A social media campaign has been launched to boost support for the event, with the Government asking people to share the hashtag #GirlSummit.