The case helped lead to a shake-up in the way French police investigate serial murders, including the improvement of co-ordination between different authorities.
Fourniret, 66, will be able to seek a reduced sentence only after serving 30 years in jail.
Given his age, he is unlikely to ever walk free.
The court, in the town of Charleville Meziere in northern France, ruled that Olivier, 59, must spend at least 28 years in jail for the part she played in some of the murders and a rape.
Olivier was accused of helping Fourniret select and capture targets, some of whom were first drugged and bound, and hiding their bodies.
Fourniret said he would not appeal against his sentence.
Some parents of the victims, six of whom were French and one Belgian, broke down in tears after the verdict was read, one day after the jury retired to deliberate.
Jean-Pierre Saison, father of one of the victims, said: "We will start a new life. It is a relief, but there can never be an end. I cannot look into the future. We need to put things into perspective without Celine."
The couple, linked by what prosecutors called a "criminal pact", became acquainted after Fourniret, who had a long history of rape, placed an advertisement for someone to write to while serving a prison sentence for sex crimes in the 1980s.
A series of opportunities to catch the killers were missed, including the failure to launch an inquiry into the disappearance of Isabelle Laville, the couple's first victim in 1987, despite the police lodging a kidnap report.
At the time, Fourniret, who had just been released from prison and was on probation, was living just a few kilometres away from the place where Laville disappeared.
Alain Behr, a lawyer for Laville's family, said: "There was a lost opportunity to identify the Fournirets."
The system also failed to revoke a decision to discharge Fourniret following appearances for offences in the 1990s, allowing the couple to continue carrying out their crimes.
Psychologists who examined the couple have said they were not insane and were slightly above average in intelligence.
The specialists concluded that the self-obsessed, authoritative Fourniret took a sadistic pleasure in rape and murder.
In addition to the murders for which he has been sentenced, Fourniret is suspected by police of a number of other killings, including that of 20-year-old Briton Joanna Parrish in 1990, raising the possibility of further trials.
A Belgian police officer told the Reuters news agency, that inquiries should be made into the murder or disappearance of about 10 people to assess possible links to Fourniret.