All five defendants in the trial were convicted of premeditated murder, with the hitman getting the stiffest sentence, life imprisonment.
Patrizia Reggiani, dubbed the "black widow" by Italy's press, blinked a few times when the judge read out her sentence for the murder of her former husband, then lowered her head.
Gucci, the last of his family to hold a stake in the maker of luxury loafers, handbags and other accessories with the double-G logo, was shot four times as he walked into his office building on 27 March 1995.
Reggiani, 49, paid the four co-defendants to eliminate Gucci, whom she had publicly made it clear she despised. She was painted as a greedy woman who was not content with her pounds 518,000-a-year alimony and feared that Gucci's new companion would devour his wealth.
Earlier in the day, when Judge Renato Semek Ludovico allowed the defendants one last plea to the jury, Reggianideclared: "I was naive to the point of stupidity," renewing her denial that she had ordered the killing.
Reggiani and the gunman, Benedetto Ceraulo, a former mechanic, maintained their innocence; the other three defendants confessed.
The three included Reggiani's former best friend, Giuseppina Auriemma, a psychic whom Gucci's former wife asked to organise the killing. She was sentenced to 25 years.
Also convicted were Ivano Savioni, a doorman in a rundown hotel in Milan's prostitution district who acted as the go-between, and the driver of the getaway car, Orazio Cicala, whose failed pizzeria and gambling habits left him in debt. Savioni was sentenced to 26 years and Cicala to 29.
Throughout the trial, Reggiani showed no remorse for Gucci's end. She had grown wan since the trial began in May, and most of her emotion came as bitterness for Auriemma's betrayal.
Reggiani admitted that she had wanted Gucci dead but argued that Auriemma converted her well-known hatred toward him into an excuse to blackmail her. "Never let the friendly fox into your chicken coop. Sooner or later, it could get hungry," she said as she began her final plea to the court.
Payments totalling pounds 226,000 made to co-defendants, she argued, were really blackmail money for a murder that she desired but did not order.
With its courtroom revelations about greed, betrayal and shameless social climbing, the trial exposed a seamy side of the chic capital of Italy's fashion industry. The Guccis had long left the fashion business, however. Gucci had old the last family stake in the company in 1993 for pounds 72m after a long history of family infighting.
Defence lawyers said that there would be an appeal. "The fact that she was sentenced to less than life imprisonment means there was some doubt," Reggiani's lawyer said.
Convicted prisoners in Italy are often released after serving just two- thirds of their sentence, meaning, along with time in custody since her January 1997 arrest, Reggiani could end up serving less than 18 years.
Reggiani's mother and one of her two daughters, Allegra, 17, were in court before the jury recessed for its seven-hour deliberations yesterday No members of the family was present for the verdict, however. Allegra broke into tears at the news, her mother's lawyer said.
The jury also awarded pounds 73,000 in damages to the Gucci office doorman, Giuseppe Onorato, who was shot in the arm while sweeping leaves near the entrance when his boss was killed.