The year 621 BC was a year of the pre-Julian Roman calendar. In the Roman Empire, it was known as year 133 Ab urbe condita . The denomination 621 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

• Draco's laws, the first written laws for Athens (approximate year)^[1]

• Duke Mu of Qin, ruler of Qin (state)
• Duke Xiang of Jin, ruler of Jin (state)
• Zhan Huo, Chinese governor