April 20, 2009 (Monday)
- The United States commemorate the 10th anniversary of the Columbine High School massacre in 1999 by Eric Harris and Dylan Klebold.
- The 2009 Pulitzer Prizes are announced. (New York Times)
- Oracle Corporation purchases Sun Microsystems for $7.4 billion. (MarketWatch)
- India's Space Research Organization launches its RISAT-2 reconnaissance satellite. (CNN-IBN)
- The National Unity Party wins Northern Cyprus's legislative election. (BBC)
- The hijacker of CanJet Flight 918 surrenders and releases his six hostages. (BBC) (Sky News)
- Durban Review Conference:
- The United Nations World Conference against Racism begins in Geneva, Switzerland. (Telegraph)
- A protester throws an object at Iranian President Mahmoud Ahmadinejad and yells, "Racist, racist!" (BBC)
- Several delegations exit during an anti-Israel speech by President Ahmadinejad. (Reuters) (Telegraph)
- China's government discovers 3,850 kilometres (2,390 mi) more of the Great Wall of China. (BBC)