In British politics, Blairism is the political ideology of Tony Blair, the former leader of the Labour Party and Prime Minister between 1997 and 2007, and those that support him, known as Blairites. It entered the New Penguin English Dictionary in 2000. Elements of the ideology include investment in public services, expansionary efforts in education to encourage social mobility, and increased actions in terms of mass surveillance alongside a ramping up of law enforcement powers, both of these latter changes advocated in the context of fighting organised crime and terrorism. Blairites have additionally been known for their contrast with the traditional support for socialism by those believing in left-wing politics, with Blair himself and others speaking out against the nationalisation of major industries and against also heavy regulations of business operations. On foreign policy, Blairism is supportive of close relations with the United States and liberal interventionism, including advocacy for both the Iraq war and the War in Afghanistan (2001–2021).

Politically, Blair has been identified with record investment into public services, an interventionist and Atlanticist foreign policy, support for stronger law enforcement powers, a large focus on surveillance as a means to address terrorism and a large focus on education as a means to encourage social mobility. In the early years (circa 1994–1997), Blairism was also associated with support for European integration and particularly British participation in the European single currency, though this waned after Labour took office.

The term is used in particular in contrast to Brownite, to identify those within the Labour Party who supported Gordon Brown rather than Blair. However, with Blair and Brown typically in agreement on most political issues (from Iraq to public sector reform), some commentators have noted that "the difference between Brownites and Blairites [...] is more tribal than ideological". This is believed to stem from a personal disagreement between Blair and Brown over who should run for the leadership following the death of John Smith in 1994. Though Brown was originally considered the senior of the two, he waited until after Smith's funeral to begin campaigning, by which point Blair had gathered too much momentum to be defeated. However, in his book Whatever it Takes, Steve Richards offered an alternate view: that there were significant disagreements between the two about relative poverty, the level of public spending and the potential for choice in public services.

In a 1999 article, The Economist stated:

Mr Blair will doubtless do his duty and lavish praise on Labour's glorious past. But, in truth, Mr Blair has always displayed a marked ambivalence towards Labour history. His greatest achievement in opposition was to get the party to ditch their historic commitment to nationalisation, and to water down its traditional links with the unions. At times he has even hinted that the very foundation of the Labour Party was a mistake, since it divided "progressive" politics and led to a century dominated by the Conservatives. Mr Blair knows that all this makes many of his party faithful deeply uneasy.

Blair's tenure is known for an expansion of LGBT rights, such as the introduction of civil partnerships. Blair told the LGBT organisation Stonewall that "what has happened is that the culture of the country has changed in a definable way" and that "it's a thing that doesn't just give me a lot of pride, but it has actually brought a lot of joy". Blair has also stated that he got up off his seat and danced upon seeing the first civil partnership ceremonies on television.

The Daily Telegraph stated in April 2008 that Blair's programme, with its emphasis on "New Labour", accepted the free-market ideology of Thatcherism. The article cited deregulation, privatisation of key national industries, maintaining a flexible labour market, marginalising the role of trade unions and devolving government decision making to local authorities as evidence. He also sought a closer, better relationship with Europe, and considered joining the Euro currency, but Gordon Brown was not in favour.

In the BBC Four documentary film Tory! Tory! Tory!, Blair is described as personally admiring Margaret Thatcher deeply and making the decision that she would be the first outside person he formally invited to visit him in 10 Downing Street.