The 2nd century is the period from 101 to 200 in accordance with the Julian calendar in the Christian/Common Era. It is considered part of the Classical era, epoch, or historical period

Early in the century, the Roman Empire attained its greatest expansion under the emperor Trajan, but after his death became primarily defensive for the rest of its history. Much prosperity took place throughout the empire at this time, ruled as it were by the Five Good Emperors, a succession of just and able rulers. This period also saw the removal of the Jews from Jerusalem during the reign of Hadrian after Bar Kokhba's revolt. The last quarter of the century saw the end of the period of peace and prosperity known as the Pax Romana at the death of the emperor Marcus Aurelius, last of the "Five Good Emperors", and the accession of his ineffective and deranged son Commodus.

Although the Han Dynasty of China was firmly cemented into power and extended its imperial influence into Central Asia during the first half of the century, by the second half there was widespread corruption and open rebellion. This set in motion its ultimate decline, until it was overthrown in 220.