Scheduled Monuments (also known as Scheduled Ancient Monuments, or SAMs) are sites of archaeological importance with specific legal protection against damage or development. The list of such sites in Wales is maintained by Cadw: Welsh Historic Monuments, an Executive Agency within the Welsh National Assembly. For an archaeological site in Wales to be scheduled it must be a site of national importance, being a site that characterises a period or category in Welsh history, with consideration given to rarity, good documentation, group value, survival/condition, fragility/vulnerability, diversity and potential. In addition to the scheduling information that Cadw maintains, there are much larger pools of information on scheduled and other archaeological and historic sites, buildings and landscapes of Wales held by the Royal Commission on the Ancient and Historical Monuments of Wales and the four Welsh Archaeological Trusts.
On the list produced by Cadw dated May 2012, there were 4,186 Scheduled Monuments in Wales, distributed among all 22 principal areas of Wales. 39 sites cross a border between two authorities, (ridge-top cairns, bridges and aqueducts, cross dykes, tramroads) so are included in both lists. The lists below show these sites, arranged by principal areas (Counties and County boroughs), and in the case of the larger counties, sub-divided to maintain a manageable number of sites per page.