The 1st century was the century spanning AD 1 (represented by the Roman numeral I) through AD 100 (C) according to the Julian calendar. It is often written as the or to distinguish it from the 1st century BC (or BCE) which preceded it. The 1st century is considered part of the Classical era, epoch, or historical period. The Roman Empire, Han China and the Parthian Persia were the most powerful and hegemonic states.

During this century, the Roman Empire (ruled by the Julio-Claudian and Flavian dynasties) continued to be in a period of relative stability known as Pax Romana, notwithstanding a financial crisis in 33 and a civil war in 69. In Europe, Rome expanded into Britain and fought wars in Germania and Dacia. In Africa, Rome was challenged by Tacfarinas, who led his own Musulamii tribe and a loose and changing coalition of other Berber tribes before being defeated in 24. In West Asia, Rome defeated a Jewish rebellion (66–73) and fought a war with Parthia from 58–63, though the latter conflict was inconclusive. In East Asia, the Chinese Western Han dynasty was overthrown and replaced by the Xin dynasty in 9, which in turn faced its own rebel movements (namely the Red Eyebrows and Lulin), and was replaced by the Eastern Han Dynasty in 25. The Eastern Han dynasty then faced and quelled a rebellion by the Trưng sisters (40–43). In 58, the Eastern Han dynasty entered a golden age with the Rule of Ming and Zhang, who were generally regarded as able administrators who cared about the welfare of the people and who promoted officials with integrity. On its northern frontier, the Chinese dynasties waged intermittent war with the Xiongnu before emerging victorious in 91. The states of Funan and Xianbei were also established in this century.

The century saw the emergence of Christianity. In the early 30s, Roman governor Pontius Pilate sentenced Jesus to crucifixion; his suffering and redemptive death by crucifixion would become central aspects of Christian theology concerning the doctrines of salvation and atonement. Anti-Jewish riots broke out in Alexandria in 38. In 64, the Great Fire of Rome destroyed two-thirds of the city, precipitating the empire's first persecution of Christians, who were blamed for the disaster. Later in 70, the siege and subsequent sack of Jerusalem and the Second Temple during the First Jewish–Roman War marked a major turning point in Jewish history. The loss of mother-city and temple necessitated a reshaping of Jewish culture to ensure its survival. Judaism's Temple-based sects, including the priesthood and the Sadducees, diminished in importance. Second Temple Judaism came to an end, while a new form of Judaism that became known as Rabbinic Judaism developed out of Pharisaic school. Furthermore, the White Horse Temple, the first Buddhist temple in China, was traditionally constructed in 68, though it is not recorded in contemporary sources before 289.