"It is a violent, brutal, terrorizing weapon," said Jolie to a committee of the House of Lords in England on Tuesday.
Jolie urged a "very strong response" to the crisis.
Thousands of women and girls have been abducted, raped and sold into sexual slavery by ISIS since they declared a caliphate across swathes of Syria and Iraq in 2014.
"ISIS is using rape as a policy in Iraq and Syria."
"They are saying: 'You should do this, this is the way to build a society, we ask you to rape,'" Jolie said.
"We really have to have a very strong response at this time to this particular group," Jolie said.
Nearly four million Syrians have fled the conflict into neighboring countries. Jolie paid 11 visits to Syrian refugees in the region since the crisis began in 2011.