Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar.

2003 has been designated as:

• International Year of Freshwater.
• European Disability Year.
• Year of the Sheep in the Chinese Zodiac.

Also see: the almanac of events for this year.

January

• January 1 - Pascal Couchepin becomes President of the Confederation in Switzerland.
• January 3 - The Ohio State University defeats the University of Miami in double-overtime in the Fiesta Bowl, 31-24, for the national Bowl Championship Series (BCS) title.
• January 3 - The 108th United States Congress is sworn in, including incoming freshmen Senators Saxby Chambliss (R-GA), Lindsey Graham (R-SC), John Sununu (R-NH), Lamar Alexander (R-TN), Elizabeth Dole (R-NC), Norm Coleman (R-MN), and Mark Pryor (D-AR).
• January 8 - US Airways Express Flight 5481 crashes at Charlotte/Douglas International Airport in Charlotte, North Carolina, killing all 21 people aboard.
• January 15 - Eldred v. Ashcroft: The Supreme Court of the United States allows the extension of copyright terms in the U.S.
• January 18 - The Canberra Bushfires occur in Canberra, Australia, killing 4 people.
• January 23 - Last signal is received from NASA's Pioneer 10 spacecraft when it is 7.5 billion miles from Earth.
• January 24 - The new United States Department of Homeland Security begins operation.
• January 25 - A Central Line train crashes into the tunnel wall at Chancery Lane tube station in London, injuring 34 people.
• January 25 - An international group of volunteers leaves London for Baghdad to act as voluntary human shields, hoping to avert a U.S. invasion.
• January 26 - Super Bowl XXXVII: The Tampa Bay Buccaneers defeat the Oakland Raiders 48-21.
• January 29 - Riots in Phnom Penh, Cambodia where the Thai Embassy was burned and commercial properties of Thai businesses were vandalized.
• January 30 - Iraq disarmament crisis: The leaders of the United Kingdom, Czech Republic, Denmark, Hungary, Italy, Poland, Portugal, Romania and Spain release a statement, The Letter of the Eight, demonstrating support for the United States' plans to invade Iraq.

February

• February 1 - STS-107, Space Shuttle Columbia disintegrates over Texas upon reentry, killing all 7 astronauts onboard.
• February 1 - In Northern Ireland, Protestant Ulster Defence Association Belfast leader John Gregg is killed by a loyalist faction.
• February 5 - Iraq disarmament crisis: U.S. Secretary of State Colin Powell addresses the UN Security Council on Iraq.
• February 7 - Unsuccessful contact attempt with Pioneer 10.
• February 9 - The Cricket World Cup begins in South Africa.
• February 9 - BBC Choice closes for the final time at 12:30 am, replacing with BBC Three at 7 pm.
• February 15 - Global protests against Iraq war: More than 10 million people protest in over 600 cities worldwide, the largest war protest to take place before the war occurs.
• February 18 - An arsonist destroys a train in Daegu, South Korea, killing more than 190.
• February 20 - The Station nightclub fire in West Warwick, Rhode Island claims the lives of 100 people.
• February 26 - An American businessman is admitted to the Vietnam France Hospital in Hanoi, Vietnam with the first identified case of SARS. WHO doctor Carlo Urbani reports the unusual highly contagious disease to WHO. Both businessman and doctor later die of the disease.