The first millennium is a period of time that commenced on January 1, 1 AD, and ended on December 31, 1000, of the Julian calendar. This millennium is the beginning of the Anno Domini/Common Era for this calendar.

In Mesoamerica, the first millennium was a period of enormous growth known as the Classic Era (200 CE – 900 CE). Teotihuacan grew into a metropolis and its empire dominated Mesoamerica. In South America, pre-Incan, coastal cultures flourished, producing impressive metalwork and some of the finest pottery seen in the ancient world.

In North America, the Mississippian culture rose at the end of the millennium in the Mississippi and Ohio river valleys. Numerous cities were built by the people, who accumulated agricultural surpluses with the cultivation of maize. Cahokia, the largest, was based in present-day Illinois, and may have had 30,000 residents at its peak about 1250 CE. It was a regional chiefdom, a political and religious center, with a trading network and influence reaching from the Great Lakes to the Gulf of Mexico. The people built a series of platform and other shaped earthwork mounds that constituted the largest earthworks north of Mexico. The circumference of the 10-story high Monks Mound at Cahokia was larger than that of the Pyramid of the Sun at Teotihuacan or the Great Pyramid in Egypt.

In Eastern Asia, the first millennium was also a time of great cultural advances. In Japan, a sharp increase in population followed when farmers' use of iron tools increased their productivity and crop yields. The Yamato court was established. The adoption of Buddhism and Confucianism contributed significantly to Japan's artists, social and political transformations.

In Western Asia, the first millennium saw a time of great advancement known as the Islamic Golden Age (700–1200 C.E).

In Europe, the first millennium was a time of great transition. The Fall of Rome in 476 CE brought an end to Classical antiquity and ushered in the Early Middle Ages. This was a period of great migrations, including the Viking expansion.
World population, which had tripled over the preceding millennium, grew more slowly during the first millennium and may have diminished. One optimistic estimate is that the world's population rose from approximately 170 to 300 million, but other estimates vary; one estimate suggests that the world population actually declined from 400 million people to 250 million people.

Civilizations, kingdoms and dynasties

The civilizations, kingdoms and dynasties in this section are organized according to the United Nations geoscheme

Events

The events in this section are organized according to the United Nations geoscheme

Significant people

The people in this section are organized according to the United Nations geoscheme

Inventions, discoveries, introductions

Centuries and decades