A jury at London's High Court has ruled that Princess Diana and her lover Dodi al-Fayed were killed by the "grossly negligent" driving of chauffeur Henri Paul.
The jury, which had listened to about 250 witnesses from around the world, also blamed the paparazzi photographers that pursued their limousine in a Paris road tunnel in 1997.
Lord Justice Scott Baker, the presiding judge, had specifically instructed the jury to reject conspiracy theories that the accident was staged.
The inquest into Diana's death, estimated to have cost up to $20m, began almost six months ago.
Conspiracy theories
Mohamed al-Fayed, Dodi's father and the owner of London's Harrod's department store, had charged that his son and Diana were killed by British security services on the orders of Prince Philip, Queen Elizabeth's husband and Diana's former father-in-law.
Fayed said her killing was ordered because the royal family did not want the mother of the future king having a child with his son who was a Muslim.
He alleged that Diana's body was embalmed to cover up evidence that she was expecting a baby.
But Scott Baker said Fayed's conspiracy theory was "without substance".
Few details of Diana's private life were spared as friends, family, faith healers, spies, bodyguards, police chiefs and butlers were called to give their opinion at an inquest that sparked worldwide media interest.
The inquest was delayed for ten years because Britain had to wait for
the French legal process and then a British police investigation to run their course before it could begin.
Both police inquiries concluded the crash was a tragic accident caused by Paul, who was said to be drunk and driving too fast.
Paul was employed by Fayed at his Ritz Hotel in Paris.
Laurence Lee, Al Jazeera's correspondent in London said: "Despite the severity of these findings there is no prospect of anyone facing any criminal charges as a result of the deaths."