The Chalcolithic (Greek khalkos + lithos 'copper stone') period or Copper Age period [also known as the Eneolithic (Æneolithic)], is a phase in the development of human culture in which the use of early metal tools appeared alongside the use of stone tools.

The period is a transitional one outside of the traditional three-age system, and occurs between the Neolithic and Bronze Age. It appears that copper was not widely exploited at first and that efforts in alloying it with tin and other metals began quite soon, making distinguishing the distinct Chalcolithic cultures and later periods difficult. The boundary between the copper and bronze ages is indistinct, since alloys sputtered in and out of use due to the erratic supply of tin.

The emergence of metallurgy occurred first in the Fertile Crescent, where it gave rise to the Bronze Age in the 4th millennium BC. There was an independent and limited invention of copper and bronze smelting by the Incas in South America and Mesoamerican civilization in West Mexico (see Metallurgy in pre-Columbian Mesoamerica).

The literature of European archaeology generally avoids the use of 'chalcolithic' (they prefer the term 'Copper Age'), while Middle-Eastern archaeologists regularly use it. The Copper Age in the Middle East and the Caucasus begins in the late 5th millennium BC and lasts for about a millennium before it gives rise to the Early Bronze Age. Transition from the European Copper Age to Bronze Age Europe occurs about a millennium later, between the late 4th and the late 3rd millennia BC.

According to Parpola, ceramic similarities between the Indus Civilization, southern Turkmenistan, and northern Iran during 4300–3300 BC of the Chalcolithic period (Copper Age) suggest considerable mobility and trade.

Europe

Ötzi the Iceman, found in the Ötztal Alps and whose remains dated about 3300 BC was found with a copper axe, which indicates that copper mining existed in Europe at least 5,300 years ago (500 years earlier than previously believed).

In Serbia a copper axe was found at Prokuplje, which indicates that human use of metals started in Europe around 7,500 years ago (~5,500BCE), many years earlier than previously believed.

Knowledge of the use of copper was far wider spread than the metal itself. The European Battle Axe culture used stone axes modelled on copper axes, with imitation "mold marks" carved in the stone.

Examples of Chalcolithic cultures in Europe include Vila Nova de São Pedro and Los Millares on the Iberian Peninsula. Pottery of the Beaker people has been found at both sites, dating to several centuries after copper-working began there. The Beaker culture appears to have spread copper and bronze technologies in Europe, along with Proto-Indo-European languages.
thumb|Chalcolithic copper mine in Timna Valley, [[Negev Desert, Israel.]]

Egypt

Remarkably the copper age in Egypt lasted well into the Middle Kingdom with bronze only becoming popular during the Eighteenth Dynasty.

South Asia

The South Asian inhabitants of Mehrgarh fashioned tools with local copper ore between 7700–3300 BC.Possehl, Gregory L. (1996)

East Asia

5th millennia BC copper artifacts start to appear in East Asia, such as Jiangzhai and Hongshan culture, but those metal artifacts were not widely used.

Mesoamerica

Less commonly, the term is also applied to American civilizations which already used copper and copper alloys thousands of years before European conquest. The Old Copper Complex, located in present day Michigan and Wisconsin in the United States used copper for tools, weapons and other implements. Artifacts from these sites have been dated from 4000 to 1000 BC, making them some of the oldest Chalcolithic sites in the entire world.