Operation Ore was a British police operation that commenced in 1999 following information received from US law enforcement, which was intended to prosecute thousands of users of a website reportedly featuring child pornography. It was the United Kingdom's biggest ever computer crime investigation, leading to 7,250 suspects identified, 4,283 homes searched, 3,744 arrests, 1,848 charged, 1,451 convictions, 493 cautioned and 140 children removed from suspected dangerous situations and an estimated 33 suicides. Operation Ore identified and prosecuted some sex offenders, but the validity of the police procedures was later questioned, as errors in the investigations resulted in many false arrests.

Operation Ore followed a similar crackdown in the United States, called Operation Avalanche; in the US, 100 people were charged from the 35,000 US access records available. In total, 390,000 individuals in over 60 countries were found to have accessed material in the combined investigations.

Between 1999 and 2001, after a tip, a US investigation was conducted into Landslide Productions Inc., a Texas-based online pornography portal operated by Thomas and Janice Reedy. The portal was found to have provided access to child pornography, and the Reedys were both convicted of trafficking child pornography in August 2001.

Following the investigation and conviction, "Operation Avalanche" was launched in the US to trace and prosecute child pornography users identified in the Landslide database. In addition, the website was run for a short time as part of a sting operation by the FBI to capture new suspects. The FBI also passed identities from the Landslide database to the police organisations of other countries, including 7,272 names to the UK.

In May 2002, Operation Ore was implemented in the UK to investigate and prosecute the Landslide users whose names were provided by the FBI. Those under investigation were reported by Rebecca Smithers of The Guardian to include government ministers, MPs, and judges.

The charge of possession of child pornography was used where evidence was found, but the lesser charge of incitement was used in those cases where a user's details were on the Landslide database but no images were found on the suspect's computer or in their home. Because of the number of names on the FBI list, the scale of the investigation in the UK was overwhelming for the police, who appealed to the government for emergency funding for the case. Reportedly, several million pounds were spent on the investigations, and complaints mounted that other investigations were put at risk because of the diversion of the resources of child protection units into the case.

Information from the Operation Ore list of names was leaked to the press early in 2003. After obtaining the list, The Sunday Times stated that it included the names of a number of prominent individuals, some of which were later published by the press. The Sunday Times reported that the list included at least twenty senior executives, a senior teacher at a girls' public school, personnel from military bases, GPs, university academics, and civil servants, a famous newspaper columnist, a songwriter for a pop band, a member of a chart-topping 1980s cult pop group, and an official with the Church of England. An investigation followed the leak, and police complained that the advance warning would allow suspected paedophiles to dispose of evidence. A police officer was reported to have lost his job for leaking the names.

After 2003, Operation Ore came under closer scrutiny, with police forces in the UK being criticised for their handling of the operation. The most common criticism was that they failed to determine whether or not the owners of credit cards in Landslide's database actually accessed any sites containing child abuse images, unlike in the US, where it was determined in advance whether or not credit card subscribers had purchased child abuse material. Investigative journalist Duncan Campbell exposed these flaws in a series of articles in 2005 and 2007.