Angelina Jolie and Foreign Secretary William Hague are to co-chair the largest gathering ever brought together on the subject of sexual violence in conflict.
The global summit - End Sexual Violence in Conflict (ESVC) - is a four-day event and it begins today at the ExCel conference centre in London Docklands.
Along with Mr Hague, Hollywood star Jolie, who is the Special Envoy for the UN Commissioner for Refugees, will today open the Global Summit Fringe, which aims to increase awareness of sexual violence in conflict.
They will also take part in meetings with youth delegates, the Foreign Office said.
Tomorrow they will attend an event to launch an International Protocol to help strengthen prosecutions for rape in conflict.
On Thursday, delegations from over 100 countries will attend and Mr Hague will chair a ministerial meeting on security in northern Nigeria.
On Friday, Mr Hague, Jolie, the UN Secretary General Ban Ki Moon (by video message) and US Secretary of State John Kerry will speak in a closing plenary session.
From Tuesday to Thursday there will be over 140 free events open to the public.
Events and performances include the Royal Court Theatre presenting the world premiere of award-winning Liberian Girl.
There will be an exclusive screening of In the Land of Blood and Honey, with the opportunity to hear its director Jolie and Mr Hague discuss the film and how it inspired the initiative that led to the summit.
As part of the 'TimetoAct' campaign, a short animation has been produced to portray the horror of rape and sexual violence through the eyes of a child.