Specialist schools in the United Kingdom (sometimes branded as specialist colleges in England and Northern Ireland) are schools with an emphasis or focus in a specific specialised subject area, which is called a specialism, or alternatively in the case of some special schools in England, in a specific area of special educational need. They intend to act as centres of excellence in their specialism and, in some circumstances, may select pupils for their aptitude in it. Though they focus on their specialism, specialist schools still teach the full curriculum. Therefore, as opposed to being a significant move away from it, the specialism is viewed as enriching the original curricular offer of the school.

Devolution has led to different policies and concepts around specialist schools in each of the four constituent countries of the United Kingdom. In England, a near-universal specialist system of secondary education has been established, with the majority of secondary schools (3,000 or 90%) specialising in one or more subjects as of 2019, while in Wales and Scotland a comprehensive system has been retained, with no specialist schools in Wales and few specialist schools in Scotland. There were 12 specialist schools in Northern Ireland as of 2015.

From 1993 (2006 in Northern Ireland) to 2011, specialist schools in England and Northern Ireland were granted additional government funding through the specialist schools programme. This programme limited the specialisms available to schools unless they had academy status, which is exclusive to England, and required them to raise money in private sector sponsorship before specialising. Since its discontinuation in 2011, the requirement of sponsorship and limitations on specialism have been lifted, but schools no longer gain extra funding for being a specialist school in those countries. In Scotland, specialist schools are directly funded by the government, unlike other schools which are funded by their local authority.

In 1998, Tony Edwards of the RISE Trust said that, in the United Kingdom, a specialist school could "simply be the neighbourhood school which has decided to emphasise a curriculum strength". In 2007, Sean Coughlan of BBC News defined specialist schools as state schools which "specialise in one or more subject areas", while Alexandra Smith of The Guardian defined them as "[s]chools that focus on a particular subject area". Channel 4 News used a similar definition to Smith's in 2010. The 2015 UK-based Oxford Dictionary of Education defines a specialist school as "[a] secondary school which specializes in the teaching of a particular area of the curriculum", while the sixth edition of Essential Public Affairs for Journalists, an Oxford University publication from 2019, concludes that specialist school is "a catch-all term embracing each and every school with a specialism" and not a particular category of school. A specialism is a specialist school's chosen subject area of focus.

Schools that gained specialist school status in the specialist schools programme could accordingly rebrand themselves as specialist schools or, alternatively, as specialist colleges. The specialist college branding was seen as a label of prestige. There were 2,000 of these specialist colleges in the United Kingdom in 2005. In the context of education after the age of 16, the term specialist college refers to institutions of further education that focus on one course or subject rather than the usual wide selection of courses. Unlike sixth form colleges with specialist school status, which still teach their specialised subject within a broader curriculum, these specialist colleges are completely based around their specialism, and their facilities and staff's specialist subject knowledge challenge those of normal schools.

Although they may be confused with each other, specialist schools have no relation to special schools. Special schools specialise in teaching special needs children rather than specific subject areas, but have been allowed to gain specialist school status since the 2000s, and many of them took an interest in possibly rebranding themselves as specialist colleges through the specialist schools programme.

Some special schools in England are now specialist schools for a specific area of special educational need. There are four possible areas to specialise in: communication and interaction, cognition and learning, social, emotional and mental health, and sensory and physical needs. To specialise in one of these areas, special schools must have pupils aged 11 and above. They cannot specialise in more than one of these areas, but can further specialise within an area to reflect the special needs they help with, for example in autistic spectrum disorders or in visual impairment.

In the private sector of education, there are specialist schools for the performing arts such as theatre and stage schools. There were 11 specialist theatre schools in the United Kingdom in 2014, with most of these being in London or its surrounding areas. In 2015, none of these schools were in Scotland, Wales and Northern Ireland, and neither were there any in the North East and South West of England, so most pupils had to relocate if they wished to attend one. There are also specialist preparatory schools in England.