The summit is the largest ever gathering of its kind, with more than 140 countries taking part.
It will be chaired by actress Angelina Jolie, who is also a UN special envoy, and the Foreign Secretary William Hague.
Jolie told the first day of the conference, which runs until Friday, it was a myth rape was "an inevitable part of conflict."
"It is a weapon of war aimed at civilians."
"It has nothing to do with sex - everything to do with power" she said.
A number of Christian charities are taking part including Restored.
Co-Director Mandy Marshall spoke to Premier.
Every year, 150 million girls and women and 70 million men and boys are raped in conflict around the world.
The vast majority of them will never report it to the police or get justice.
Revd Dr Carrie Pemberton Ford from the Cambridge Centre for Applied Research in Human Trafficking told Premier's News Hour the Church has a vital role to play in the campaign.
The Foreign Secretary William Hague has announced and extra £6million in funding for survivors of sexual violence across the world.
Last year the G8 declared rape in war time as a grave breach of the Geneva Convention and a war crime.
Since then 144 world governments have agreed and endorsed the statement.