Jolie has campaigned against rape as a weapon of war for a decade and made a 2011 film, In The Land of Blood and Honey, about mass rapes committed during the Bosnian War in the 1990s.
She praised the British government for taking the lead on the issue.
"What it means to be here with you at this committee, in your Parliament, knowing you are studying the best ways to help these women - I think that speaks to young women about their value, I'm very happy to be here," Jolie told members of the select committee on Sexual Violence in Conflict.
She described some of the victims she had met - women, children and men - who have been raped in war zones.
"For over ten years I had been visiting the field and meeting with families and survivors of sexual violence who felt for so long that their voices simply didn't matter - they weren't heard and they carried a great shame.
"I remember distinctly meeting this little girl, who was very young - probably about seven or eight - and she was rocking backwards and forwards and staring at the wall and tears were streaming down her face because she had been brutally raped multiple times.
"You couldn't talk to her, you couldn't touch her. I felt absolutely helpless and din't know what to do for her.
"More recently I met a 13-year-old girl in Iraq who had been kept in a room with many other girls and they were taken out in twos, brought to this very dirty room with this dirty couch and raped repeatedly.
"But they told me what was even worse than the physical violence was that they then had to stand in rooms and watch their friends be sold and to hear men arguing what they were worth - $40, $50. What was the price of them? What was their value?"
She also told the story of a Syrian doctor and his family who fled their homeland for Libya, only to live in fear that his wife and daughters would be sexually assaulted in a camp. The family decided to escape by making a perilous journey across the Mediterranean, but died in the crossing.
Explaining why she joined forces with Hague, Jolie said of her film: "I certainly did my best but felt very limited as an artist. We could express certain things and get people around the world feeling outraged or to condemn it, but it really has been a change in my view of the world, working closely with the government of the UK - realising that for all that wonderful goodwill, laws need to change, policy needs to change, governments and leadership needs to come together and that's what will make a real difference."
Hague told the committee that Jolie's international celebrity had helped to put the issue on the global stage.
He said: "When Angelina made her film The Land of Blood and Honey, my special advisor at the time persuaded me to watch it and show it in the Foreign Office and that was what brought us together in PSVI.
"NGOs have done fantastic work and the real heroes are the hospital workers, the people who support survivors. But what was missing was a major country in the world using its seat at the United Nations and its diplomatic reach to raise this subject around the world.
"The other thing missing was the global reach which Angelina Jolie-Pitt has brought to help people all over the world see what an important subject it is. They were the two missing ingredients."
