21st century BC

The 21st century BC is a century which lasted from the year 2100 BC to 2001 BC.

 Events 

 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.
 c. 2064 BC – 1986 BC: Twin Dynasty wars in Egypt.
 c. 2055 BC: End of First Intermediate Period of Egypt.
 c. 2055 BC: Middle Kingdom began in Ancient Egypt.
 c. 2055 BC: Mentuhotep II from Thebes got Ancient Egypt together.  He 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 City.
 c. 2049 BC: Oak trees for Seahenge felled.
 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. 2004 BC: Pharaoh Mentuhotep II, Eleventh dynasty of Egypt dies.
 c. 2000 BC: Aegean Bronze Age ended.

 Significant persons 

 Ur-Nammu, 3rd dynasty of Ur
 Shulgi of Urim

Legendary people

 According to Abrahamic religious tradition, the era of the Patriarch Abraham (however, other dates 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 law code in Mesopotamia, the Code of Ur-Nammu
2037 BC—Emperor Shen Nong makes first (perhaps mythical) tea drink by boiling fresh leaves