In the United Kingdom, a scheduled monument is a nationally important archaeological site or historic building, given protection against unauthorised change.

The various pieces of legislation that legally protect heritage assets from damage, visual disturbance, and destruction are grouped under the term "designation". The protection provided to scheduled monuments is given under the Ancient Monuments and Archaeological Areas Act 1979, which is a different law from that used for listed buildings (which fall within the town and country planning system). A heritage asset is a part of the historic environment that is valued because of its historic, archaeological, architectural or artistic interest. Only some of these are judged to be important enough to have extra legal protection through designation.

There are about 20,000 scheduled monuments in England representing about 37,000 heritage assets. Of the tens of thousands of scheduled monuments in the UK, most are inconspicuous archaeological sites, but some are large ruins. According to the 1979 Act, a monument cannot be a structure which is occupied as a dwelling, used as a place of worship or a protected shipwreck.

Scheduled monuments are defined in the Ancient Monuments and Archaeological Areas Act 1979. In England, Wales and Scotland they are often referred to as a scheduled ancient monument, although the act defines only ancient monument and scheduled monument. A monument can be:

In Northern Ireland they are designated under separate legislation and are referred to as a scheduled historic monument (for those in private ownership) or a monument in state care (for those in public ownership).

The first Act to enshrine legal protection for ancient monuments was the Ancient Monuments Protection Act 1882. This identified an initial list of 68 prehistoric sites that were given a degree of legal protection (25 sites in England, three in Wales, 22 in Scotland and 18 in Ireland). This was the result of strenuous representation by William Morris and the Society for the Protection of Ancient Buildings, which had been founded in 1877. Following various previous attempts, the 1882 legislation was guided through Parliament by John Lubbock, who in 1871 had bought Avebury, Wiltshire, to ensure the survival of the stone circle.

The first Inspector of Ancient Monuments, as set up by the act, was Augustus Pitt Rivers. At this point, only the inspector, answering directly to the First Commissioner of Works, was involved in surveying the scheduled sites and persuading landowners to offer sites to the state. The act also established the concept of guardianship, in which a site might remain in private ownership, but the monument itself become the responsibility of the state, as guardian. However the legislation could not compel landowners, as that level of state interference with private property was not politically possible. The Ancient Monuments Protection Act 1900 extended the scope of the legislation to include medieval monuments. Pressure grew for stronger legislation. In a speech in 1907, Robert Hunter, chairman of the National Trust, observed that only a further 18 sites had been added to the original list of 68. 'Scheduling' in the modern sense only became possible with the passing of the Ancient Monuments Consolidation and Amendment Act 1913.

When Pitt Rivers died in 1900 he was not immediately replaced as Inspector. Charles Peers, a professional architect, was appointed as Inspector in 1910 in the Office of Works becoming Chief Inspector in 1913. The job title 'Inspector' is still in use.