The duration of the Iron Age varies depending on the region under consideration. It is defined by archaeological convention, and the mere presence of cast or wrought iron is not sufficient to represent an Iron Age culture; rather, the term "Iron Age" implies that the production of carbon steel has been perfected to the point where mass production of tools and weapons superior to their bronze equivalents become possible. In the Ancient Near East, this transition takes place in the wake of the so-called Bronze Age collapse, in the 12th century BC. The technology soon spreads throughout the Mediterranean region and to South Asia. Its further spread to Central Asia, Eastern and Central Europe is somewhat delayed, and Northern Europe is reached still later, by about 500 BC.

Increasingly the Iron Age in Europe is being seen as a part of the Bronze Age collapse in the ancient Near East, in ancient India (with the post-Rigvedic Vedic civilization), ancient Iran, and ancient Greece (with the Greek Dark Ages). In other regions of Europe the Iron Age began in the 8th century BC in Central Europe and the 6th century BC in Northern Europe. The Near Eastern Iron Age is divided into two subsections, Iron I and Iron II. Iron I (1200–1000 BC) illustrates both continuity and discontinuity with the previous Late Bronze Age. There is no definitive cultural break between the 13th and 12th centuries BC throughout the entire region, although certain new features in the hill country, Transjordan and coastal region may suggest the appearance of the Aramaean and Sea People groups. There is evidence, however, of strong continuity with Bronze Age culture, although as one moves later into Iron I the culture begins to diverge more significantly from that of the late 2nd millennium.