A boundary marker, boundary stone or border stone is a robust physical marker that identifies the start of a land boundary or the change in a boundary, especially a change in a direction of a boundary. They have often been used to mark critical points on boundaries between countries or local administrations but have also been used to mark out the limits of private land-holdings especially in areas where fences or walls are impractical or unnecessary.
Boundary markers are often made of stone and are typically placed at a notable or especially visible point. Many are inscribed with relevant information such as the abbreviation of the boundary holder and often a date.
Boundary markers may be used to mark property boundaries (land-ownership), or political boundaries.
In developed countries use of markers for land-ownership has in many places been replaced by maps and land ownership registration. Markers are still used extensively for marking international borders; international boundary markers are placed and maintained by mutual agreement of the bordering countries.
