21st century BC
|Millennium:||3rd millennium BC|
|Decades:||2090s BC 2080s BC 2070s BC 2060s BC 2050s BC
2040s BC 2030s BC 2020s BC 2010s BC 2000s BC
|Categories:||Births – Deaths
Establishments – Disestablishments
The 21st century BC is a century which lasted from the year 2100 BC to 2001 BC.
Note: all dates from this long ago should be regarded as either approximate or conjectural; there are no absolutely certain dates, and multiple competing reconstructed chronologies, for this time period.
- c. 2100 BC – c. 2050 BC: Nanna Ziggurat, Ur (modern Muqaiyir, Iraq) was built.
- 2091 BC: Beginning of the Patriarchal Age was traditionally set in this year.
- 2080 BC: Ninth Dynasty wars in Egypt.
- 2080 BC: First Intermediate Period of Egypt ended. Middle Kingdom began in Ancient Egypt.
- 2071 BC: Magh Ithe, first recorded battle in Ireland myths.
- 2070 BC (disputable): Yu the Great set up the Xia Dynasty, which isn't verified by archeological findings, some propose the Erlitou culture.
- c. 2064 BC – 1986 BC: Twin Dynasty wars in Egypt.
- c. 2055 BC: End of First Intermediate Period of Egypt (another date is 2040 BC).
- c. 2055 BC: Middle Kingdom began in Ancient Egypt (other date is 2040 BC).
- c. 2055 BC: Mentuhotep II from Thebes managed to reunite Ancient Egypt and began to rule (other date is 2040 BC).
- c. 2055 BC – 1985 BC: Funerary Stele of Amenemhat I was made. Eleventh Dynasty of Egypt. Excavated in 1915–1916. It is now kept in Egyptian Museum, Cairo. The Metropolitan Museum of Art, New York.
- c. 2049 BC: Oak trees for Seahenge felled.
- c. 2040 BC: End of First Intermediate Period of Egypt. Start of Middle Kingdom. 11th–14th Dynasties.
- 2040 BC: Beginning of the Xia Dynasty, the first dynasty and government system in China.
- 2040 BC: Pharaoh Merykare died. End of Tenth dynasty of Egypt. Pharaoh Mentuhotep II started to rule. Start of Eleventh Dynasty.
- 2034 BC – 2004 BC: Ur–Amorite wars.
- c. 2009 BC – 1997 BC: Funerary temple of Mentuhotep III was built. Eleventh Dynasty.
- 2004 BC: Elamite destruction of Ur.
- c. 2000 BC: Aegean Bronze Age ended.
Significant persons 
Legendary people 
- According to Abrahamic religious tradition, the era of the Patriarch Abraham (however, other datings include 19th century BC, and/or 17th century through 15th century BC)
- According to Hindu tradition, lifetime of Rama, the 7th Avatar of Vishnu
Inventions, discoveries, introductions 
- 2100 BC—Earliest extant law code in Mesopotamia, the Code of Ur-Nammu
- 2037 BC—Emperor Shen Nong makes first herbal medicine named as "tea" (different from modern tea) and a few herbal poison.(perhaps mythical)
Decades and years