But it was also an incident - up there with the shooting of John F Kennedy, the death of Hitler and the moon landings - that has become the basis for countless conspiracy theories in the last 20 years.
While the official investigation ruled that the crash had been caused by Diana's chauffeur Henri Paul being under the influence of drink and prescription drugs, Mohammed Al Fayed, whose son and Diana's lover Dodi, was also killed in the crash, has maintained that the pair were murdered - and claimed there were nearly 200 conspiracies into the crash.
Here are just some of the conspiracy theories about Diana's death.
1. HENRI PAUL WAS A SECRET SERVICE AGENT
Theorists have alleged that the driver of the Mercedes, acting head of Ritz security Henri Paul, was in the pay of a national security service - either Britain, France or the United States. Al-Fayed claims that Henri Paul was working for MI6 and that they set him up. An inquiry found no evidence of a connection.
2. BLOOD SAMPLES WERE UNRELIABLE
Another allegation concerns the reliability of blood tests carried out, which indicated Paul had been drinking before he took the controls of the car. The French investigators' conclusion that Paul was drunk was made on the basis of an analysis of blood samples, which were said to contain an alcohol level that was three times the French legal limit. An expert cited in the report estimated that Paul had drunk the equivalent of ten small glasses of Ricard, his favourite liquorice-flavoured French aperitif, before driving. Theories persist that the blood samples were unreliable.
3. AN M16 COVER-UP
Richard Tomlinson, a former MI6 officer who was dismissed from the intelligence services and later served five months in prison for breaching the Official Secrets Act 1989, claimed in a sworn statement to the French inquiry in May 1999 that Britain's MI6 had been involved in the crash, He claimed that Paul was working for the security services and that one of Diana's bodyguards, either Trevor Rees-Jones or Kes Wingfield, was a contact for British intelligence.
Tomlinson alleged that MI6 was monitoring Diana before her death, had told Al-Fayed that Paul was an MI6 agent and that her death mirrored plans he saw in 1992 for the assassination of then President of Serbia Slobodan Milošević, using a strobe light to blind his chauffeur.
4. WAS DIANA PREGNANT?
One of the main motives which has been advanced for alleged murder includes suggestions Diana was pregnant with Dodi Fayed's child and the couple were about to get engaged. The alleged dislike of the idea of a non-Christian within the British Royal Family meant such a relationship between the mother of the future king and a prominent Egyptian Muslim would not be tolerated. In Al-Fayed's view, Prince Philip, the Prince of Wales, Diana's sister Lady Sarah McCorquodale and numerous others were all involved in a plot to kill the Princess and his son.
5. LACK OF CCTV
The absence of CCTV images showing the Mercedes' journey from the hotel to the crash site has been frequently cited as evidence of an organised conspiracy. In a submission to the Minister for Justice, Scotland for Public Inquiry in February 2003, Mohamed Al-Fayed stated that there were approximately 10 video cameras on the route taken by the Mercedes, including one on the entrance to the tunnel itself, yet there are no recordings from any of these cameras for the night in question. In December 2006, The Independent newspaper published an article stating there were more than 14 CCTV cameras in the Pont de l'Alma underpass, yet none have recorded footage of the fatal collision.
6. THE WHITE FIAT UNO
Analysis of the wreckage of the Mercedes revealed it had glancing contact with a white Fiat Uno car which left traces of paint on the Mercedes bodywork. Extensive attempts by the French police to find the vehicle involved were unsuccessful. Mohamed Al-Fayed alleged that the white Fiat Uno was being used by MI6 as a means of causing the Mercedes to swerve and thereby crash into the side of the tunnel. Al-Fayed further alleged that the Fiat Uno was owned by a French photojournalist named Jean-Paul James Andanson, a security services agent according to Fayed. Andanson's death in May 2000, Al-Fayed claimed, was either due to guilt over what he had done or because he was assassinated by the French or British security services to silence him.