- Jan 20 Barack Obama, inaugurated as the 44th President of the United States of America, becomes the United States' first African-American president
- Mar 4 International Criminal Court issues an arrest warrant for Sudanese President Omar Hassan al-Bashir for war crimes and crimes against humanity in Darfur becoming the first sitting head of state to be indicted
- Apr 30 Chrysler automobile company files for Chapter 11 bankruptcy
- May 18 Sri Lankan Civil War: The LTTE are defeated by the Sri Lankan government, ending almost 26 years of fighting between the two sides.
- Nov 16 "The Twilight Saga: New Moon", based on the book by Stephenie Meyer, directed by Chris Weitz, starring Kristen Stewart and Robert Pattinson, premieres in Los Angeles
- Dec 18 James Cameron's "Avatar" starring Sam Worthington, Zoe Saldana and Sigourney Weaver, released in the US, becomes highest-grossing film of all time
Gamma ray burst (GRB) 090423 is observed for 10 seconds, the most distant object of any kind and also the oldest known object in the universe
On April 23, 2009