A menhir is the simplest form of a megalithic monument. It consists of a generally elongated stone, rough or minimally carved, placed vertically and with its lower part buried in the ground to prevent it from falling.[1]​.

The term originates from France and results from the union of two words from the Breton language: maen ("stone") and hir ("long").[2] It was adopted by archaeologists in the 19th century.

The only unworked or barely worked prehistoric megalith is called a menhir. Some have engravings. Others are sculpted, often anthropomorphically, although in this case we can speak of steles "Stele (monument)") or idols and not menhirs in the strict sense. Their size varies, from small rocks that are only distinguished from other stones by being part of alignments or cromlech, to some Breton monoliths (Kerloas, Champ-Dolent, Grand Menhir Brisé) with a height of more than 10 meters.

The specific ritual meanings that inspired the erection and arrangement of the Neolithic menhirs are unknown, and more or less elaborate conjectures and with greater or lesser scientific rigor are formulated around it. It is only known for sure that they were, like other similar monuments of the time, funerary constructions. At its feet there are usually tombs with remains or ashes of the deceased, ceramics, etc. The large megalithic complexes would have been necropolises and the menhirs would have played the role of tombstones linked to the commemoration and worship of ancestors. Certain menhirs could have been tributes to the deities or, in the case of sculpted menhirs, representations of them.

A case apart are certain Christianized European menhirs whose carved crosses or biblical scenes show how this religion assimilated or reused monuments associated with previous times and beliefs.

Although they abound in Europe as a consequence of the historical phenomenon of megalithism, their geographical extension is practically global:[3] India, Syria, the Caucasus, Crimea, northern coast of the Black Sea, Bulgaria, China, Japan, Mongolia, Russia, Polynesia, North Africa, Spain, Portugal, Italy (several in Sardinia), France, Great Britain, southwestern Sweden, Denmark, Holland, Belgium, northern Germany, Australia (aboriginal megaliths), Colombia, Argentina, Venezuela, etc. They do not exist in Greece. Although originated by a different culture and in a parallel way, very ancient "menhirs" are also found in certain areas of Argentina (Los Menhires Archaeological Reserve).[4]​.