The woman's boyfriend, 34, told gardaí they were attacked by a gang of five males as they sat in a car in Cratloe Woods, Co Clare, after 4am yesterday.
The man was beaten with a golf club and then locked in the boot of the car while five males from the south side of Limerick city each raped the woman in the quiet rural wooded area just off the main Limerick to Shannon road.
The couple both live in villages in Co Clare and work in the bar trade in Limerick city.
The man later managed to free himself from the car and detain one of the attackers, despite sustaining a broken arm and several stab wounds. He called the gardaí from his mobile phone.
Two of the rape suspects were arrested in Cratloe and three others were arrested at a nearby house, where it's believed they were trying to steal a car.
They were taken to Ennis and Shannon garda stations.
Gardaí came on the scene quickly because they were investigating a robbery close by at a school in Cratloe, which occurred at around 2.30am.
Both the robbery and the alleged rape could be linked, gardaí believe.
Four of the five are under 18 years of age. They include a 14-year-old, two 15-year-olds, a 16-year-old and a man aged 22.
One of the arrested teenagers was taken by ambulance to the Mid Western Regional Hospital in Limerick after he claimed he was injured by the woman's boyfriend.
The teen then escaped from the hospital but he was re-arrested at a home in a southside housing estate in Limerick city.
The woman was treated in the sexual assault unit at the South Infirmary Hospital in Cork. She was first taken to the Mid Western Regional Hospital but had to be transferred to the specialist unit in Cork.
Her injured boyfriend was also initially treated in Limerick but he was moved to a Galway hospital last night where he received plastic surgery for an arm injury.
Chief Superintendent Liam Quinn, who is leading the investigation, described the incident as horrific.
Superintendent John Kerin said it was the most horrific case he had ever seen.
The Limerick Rape Crisis Centre yesterday called for a special sexual assault unit to be established in the city.
Rape victims have to endure a two-hour journey to Cork for treatment because there is no unit in Limerick.
"Some rape cases have not been taken because
victims just won't travel to Cork, they are often too distraught," centre spokeswoman Ingrid Wallace said.
"All someone wants to do after a rape is have a shower. But they are faced with a two-hour drive in a squad car to Cork."