Jonathon Mallon, 32, was told by judge Bill Dunlop QC that he must spend at least 10 years behind bars before being able to apply for parole.
But Judge Mallon added: "You may never be released and the prospects are that you will be in custody for a very long time indeed."
Mallon was convicted at the High Court in Glasgow of carrying out a campaign of terror against the women over a 14-year period.
Sick Mallon raped one of his victims in a Glasgow cinema toilet and another in a changing cubicle at Scotstoun swimming pool.
Mallon was convicted of the rapes, sexual abuse and domestic abuse after a lengthy trial.
His rape victims are now aged 21, 25, 26, 31, 31, and his sex abuse victim is 27. All his victims were vulnerable.
Judge Dunlop told Mallon: "This was a course of conduct that can only be described as monstrous.
"These offences were carried out against six women, each of whom was vulnerable in one way or another.
"The evidence all spoke of you meeting them, and at first you charmed them, then very quickly became controlling."
Judge Dunlop said that Mallon's victims had been left "devastated" by what he did to them.
Prosecutor Kath Harper told the court that Mallon has previous convictions for domestic abuse, violence, carrying a knife and fire raising.
Mallon, a keen churchgoer, met two of his victims at church, another he chatted up on a bus and the others he met at parties.
Mallon was described by one of his former girlfriends, who is 26, as as Jekyll and Hyde character.
In evidence, Mallon denied all the allegations against him and claimed that any sex was consensual.
He was asked why these women should make up stories about him and stated: "I don't know. I don't have an answer."
The domestic abuse and rapes took place over a 14 year period from 1999 to 2013.
The policeman who led the investigation, DI Mark McGowan, said: "Hopefully we have given these women justice."