Trained specialists will be on hand at any time by phone or online to offer emotional support and information on what other services are available.
The Government-funded helpline has been set up in time for Christmas when reports of attacks have in the past been known to increase.
Operated by Rape Crisis England and Wales, the service can be used by anyone aged 16 and over who has experienced sexual violence and abuse at any point in their life, the Ministry of Justice (MoJ) said.
It is hoped providing help to victims will also bring more perpetrators to justice, as Independent Sexual Violence Advisers (ISVAs) are among the services which the helpline would suggest for victims.
According to the MoJ, research suggests victims who speak to an ISVA are less likely to withdraw from the criminal justice process.
Justice Secretary Dominic Raab said: “Making sure that victims of rape and sexual abuse have support whenever they need it is not only the right thing to do – it will also help us to bring more perpetrators to justice.
“When victims feel believed and supported, they are much more likely to stay the course in the criminal justice process.
“This vital helpline will have a major role to play in providing the support victims need, and in bringing more vile criminals to justice.”
Rape Crisis chief executive Jayne Butler said the charity was “proud” to be offering the helpline, adding: “No matter when or where it happened – we are here for you. If you contact us we will always listen to you and believe you, and we will never judge.”
The boss of Women’s Aid, Farah Nazeer, welcomed the move and said: “We hope this will ensure survivors get the right response, first time – which we know is key to recovery after abuse. We’re hopeful this will also lead to an improvement in reporting and convictions of sexual offences.”
But Labour’s shadow justice secretary Steve Reed said: “It’s embarrassing that after 12 years, a belated helpline is all the Tories can come up with to address their abysmal record on violence against women and girls.
“In the 18 months it’s taken ministers to act since the hotline was announced, more than 70,000 victims have reported they have been raped. These delays do nothing to prevent sexual violence or ensure that victims get justice.”
The MoJ said it wanted to make sure the helpline worked properly and had sufficient staffing levels before it was launched.
The department also highlighted how this was the latest measure in a range of work to better support victims and tackle violence against women and girls, including quadrupling funding for services, bringing forward law changes with the Victims Bill, a pilot offering specialist sexual violence support in crown courts and allowing complainants to pre-record evidence for criminal cases.
To contact the helpline, dial 0808 500 2222 or visit www.247sexualabusesupport.org.uk