The People's Pledge was a political campaign to secure a referendum on the United Kingdom's membership of the European Union. It aimed to achieve this by asking voters to sign a pledge that they would use their vote to help secure a majority of Members of Parliament (MPs) in support of an in-out referendum on EU membership. The 1975 European Communities membership referendum was the last time such a vote had occurred in Britain.

The campaign did not take a view on whether the UK should stay in, or leave, the EU; simply that the expansion of the EU's powers and influence over government since the 1975 'common market' referendum merited people being consulted again on continued membership. According to the Labour Party MP Kelvin Hopkins: "While those who initiated the People's Pledge campaign are primarily Eurosceptic, it has support from those who take a different, pro-EU view, but who wish to see the issue properly resolved by a vote of the British people."

Directed at its launch by Mark Seddon, with cross-party support from MPs including the Labour party's head of policy Jon Cruddas MP and other politicians including then Mayor of London Boris Johnson, it aimed in particular to focus pressure on MPs in marginal seats using the tactic of holding independently scrutinised constituency referendums. By early 2012, more than 128,000 voters and 87 MPs had signed up to the campaign. In September 2012, the People's Pledge was appointed as the secretariat to a new APPG for an EU referendum, with Conservative MP John Baron acting as the group's chair and Labour MP and former government minister Keith Vaz as vice chair.

The campaign is credited with having had a key role in bringing about the United Kingdom European Union membership referendum, held in June 2016. Prominent Conservative MEP Daniel Hannan wrote in his 2016 book What Next? that "The People's Pledge was the most effective popular campaign I have ever been involved with, and must be reckoned one of the most successful pressure groups in British history." James Forsyth, writing in The Spectator, said that the campaign's recruitment of Boris Johnson as a supporter had made an EU referendum almost certain: "Boris Johnson's decision while campaigning last month to sign up to the campaign for an in/out referendum on EU membership could be a key moment in the history of the Conservative party – the moment when the party's balance of power tipped decisively in favour of a referendum." Along with Forsyth, Paul Goodman of ConservativeHome and Leo McKinstry of the Daily Express have cited the success of the campaign as a main reason why a referendum became a possibility.

In January 1973, on its third application, Britain was accepted into the European Economic Community. The 1975 European Communities membership referendum was held after that, following a change in government from the Conservatives under Edward Heath who had led the application process, to the minority Labour government of Harold Wilson, who had made a referendum an election promise. The referendum found 67% to be in favour, on a 65% turnout. Subsequent treaties leading to the development of the European Union were signed into law without recourse to a referendum.

According to the campaign, all three major British political parties withdrew promises of a referendum on the last major European treaty, which proposed the creation of a European Constitution, after it was re-drafted as the Treaty of Lisbon, and subsequently ratified by the UK on 19 June 2008 by the Labour Government of Gordon Brown. The subsequent 2010 general election unusually produced a hung parliament, leading to a Conservative – Liberal Democrat coalition government bound by an agreement that there would be "no further transfer of sovereignty or powers over the course of the next Parliament", and to cover for future terms, proposed the introduction of the European Union Bill 2010, which sought to "amend the 1972 European Communities Act so that any proposed future treaty that transferred areas of power, or competences, would be subject to a referendum on that treaty". The coalition did not however commit to holding a referendum on the status of the existing membership.

A YouGov poll conducted in September 2010 of 1,948 adults in the UK found that if there was a referendum on Britain's membership of the EU, 47% would vote to leave, compared to 33% who would want to remain.

The People's Pledge campaign was launched in Westminster on 15 March 2011. The campaign website had been launched two days earlier.