2009 (MMIX) is the current year of the Anno Domini/Common Era in accordance with the Gregorian calendar. It is a common year starting on Thursday and the last year of the 2000s decade.

2009 has been designated as the:

• International Year of Astronomy.
• International Year of Natural Fibres.

January

• January 1 – Austria, Japan, Mexico, Turkey, and Uganda assume their seats on the United Nations Security Council.
• January 1 – The Czech Republic takes over the presidency of the Council of the European Union from France.
• January 1 – At least 61 people are killed in a fire in Bangkok during New Year celebrations.
• January 1 – Asunción, the capital of Paraguay, becomes the American Capital of Culture and Vilnius and Linz become the European Capitals of Culture.
• January 1 – Slovakia adopts the Euro as its national currency, replacing the Slovak koruna.
• January 3 – Israel launches a ground invasion of Gaza.

• January 7 – Russia shuts off all gas supplies to Europe through Ukraine. Prime Minister Vladimir Putin publicly endorses the move and urges that international observers be brought into the energy dispute.
• January 12 – The Electronic System for Travel Authorization becomes mandatory for participating travelers from Visa Waiver Program countries in advance of travel to the United States.
• January 13 – Ethiopian military forces begin pulling out of Somalia, where they have tried to maintain order for nearly two years.

• January 15 – US Airways Flight 1549, en route to Charlotte/Douglas International Airport from New York's LaGuardia Airport, ditches in the Hudson River off Manhattan. All 155 passengers and crew are evacuated and taken to safety. The plane is apparently brought down by a flock of Canada Geese.
• January 17 – Israel declares a unilateral cease-fire against Hamas militants and puts an end to attacks after 22 days of violence in Gaza.
• January 20 – Barack Obama is inaugurated as the 44th, and first African-American, President of the United States. thumb|An explosion caused by an Israeli airstrike in Gaza during the 2008–2009 Israel–Gaza conflict
• January 22 – U.S. President Barack Obama signs an order to close Guantanamo Bay detention camp within one year.
• January 22 – Congolese rebel leader Laurent Nkunda is captured by Rwandan forces after crossing over the border into Rwanda.
• January 23 – The Japan Aerospace Exploration Agency launches the world's first-ever Greenhouse Gases Observing Satellite, "Ibuki", from Tanegashima Space Center.
• January 26 – The first-ever trial at the International Criminal Court is held. Former Union of Congolese Patriots leader Thomas Lubanga is accused of training child soldiers to kill, pillage, and rape.
• January 26 – The Icelandic government and banking system collapse; Prime Minister Geir Haarde immediately resigns.
• January 29 – An Israeli Defense Forces air raid injures nine people in the Gaza Strip in response to continued militant rocket fire.