The National Health Service (NHS) is the term for the publicly funded healthcare systems of the United Kingdom: the National Health Service (England), NHS Scotland, NHS Wales, and Health and Social Care (Northern Ireland) which was created separately and is often referred to locally as "the NHS". The original three systems were established in 1948 (NHS Wales/GIG Cymru was founded in 1969) as part of major social reforms following the Second World War. The NHS was officially launched at Park Hospital in Davyhulme, near Manchester, England (now known as Trafford General Hospital). The founding principles were that services should be comprehensive, universal and free at the point of delivery. Each service provides a comprehensive range of health services, provided without charge for residents of the United Kingdom apart from dental treatment and optical care. In England, NHS patients have to pay prescription charges; some, such as those aged over 60, or those on certain state benefits, are exempt.

Taken together, the four services in 2015–16 employed around 1.6 million people with a combined budget of £136.7 billion. In 2024, the total health sector workforce across the United Kingdom was 1,499,368.

When purchasing consumables such as medications, the four healthcare services have significant market power that influences the global price, typically keeping prices lower. A small number of products are procured jointly through contracts shared between services.