The Greensill scandal was a political controversy in the United Kingdom related to lobbying activities on behalf of financial services company Greensill Capital which was founded in 2011 by Lex Greensill. It implicated former Prime Minister David Cameron, former Cabinet Secretary Jeremy Heywood and several other civil servants, and occurred during the COVID-19 pandemic.

First reported by the Financial Times and The Sunday Times, it arose from the insolvency of the supply chain financing firm Greensill Capital in March 2021, first reported by The Wall Street Journal. Reports emerged that Cameron had lobbied Chancellor of the Exchequer Rishi Sunak in 2020 to change rules in order to allow Greensill to join the Covid Corporate Financing Facility, a government loan scheme that was initiated to support companies during the pandemic-related economic recession.

A Cabinet Office inquiry found Lord Heywood to be primarily responsible for Lex Greensill being given a role in government and access into 10 Downing Street. That inquiry and two other separate official inquiries found that Cameron had not broken any lobbying rules or acted unlawfully in relation to his Greensill lobbying activities, although a Treasury committee report said in finding he did not break lobbying rules “that reflects on the insufficient strength of the rules”.

During Cameron's 2010–2016 premiership, financier Lex Greensill, suggested by the image of a business card published by the Labour Party to be a senior advisor to the Prime Minister, was alleged by The Sunday Times to have had access to eleven departments and agencies. In 2018, Cameron became an adviser to Greensill Capital and held shares in the company. It has been reported that he may have made $60 million from a listing of the company, as well as it being reported that "people familiar with the matter" said he was being paid over $1 million a year for 25 days work per year.

Documents obtained by the BBC's Panorama suggested that Cameron earned around £7m from his salary and selling shares. In 2019, Cameron arranged for a private meeting with Lex Greensill and Secretary of State for Health and Social Care Matt Hancock. Some NHS trusts went on to use Greensill Capital's services.

In 2020, several months before Greensill Capital collapsed, Cameron lobbied the government to change the rules to allow it to join the Covid Corporate Financing Facility scheme, which would enable it to issue government guaranteed loans to support firms during the COVID-19 pandemic in the United Kingdom, which had had a major economic impact. Cameron lobbied the Chancellor of the Exchequer Rishi Sunak via a series of text messages. There was also at least one phone call between the two, the nature of which was not disclosed. Cameron's requests on behalf of Greensill were declined.

Cameron also lobbied an official of the German government on behalf of Greensill. In November 2020, he participated in a virtual call with the German ambassador alongside senior representatives from Greensill to discuss introducing its products into the German civil service.

According to Cameron, his lobbying on Greensill's behalf did not break any rule of conduct.