2004 (MMIV) was a leap year starting on Thursday (dominical letter DC) of the Gregorian calendar, the 2004th year of the Common Era (CE) and Anno Domini (AD) designations, the fourth year of the 3rd millennium, the fourth year of the 21st century, and the fifth year of the 2000s decade.
2004 was designated as:
- International Year of Rice (by the United Nations)
- International Year to Commemorate the Struggle Against Slavery and its Abolition (by UNESCO)
- 2004 World Health Day topic was Road Safety (by World Health Organization)
- January 3 – Flash Airlines Flight 604 crashes into the Red Sea off the coast of Egypt, killing all 148 aboard.
- February 1 – A hajj stampede in Mina, Saudi Arabia, kills 251 pilgrims.
- February 4 – Facebook, a mainstream online social networking site, is founded by Mark Zuckerberg.
- February 7 – Several leaders of Abnaa el-Balad are arrested in Israel.
- February 24 – The 6.3 Mw Al Hoceima earthquake strikes northern Morocco with a maximum Mercalli intensity of IX (Violent). At least 628 people are killed.
- February 26
- February 27
- February 28 – Over 1 million Taiwanese participating in the 228 Hand-in-Hand Rally form a 500-kilometre (310 mi) long human chain to commemorate the February 28 Incident in 1947.
- February 29 – 2004 Haitian coup d'état: Jean-Bertrand Aristide resigns as president of Haiti. The chief justice of the Haitian Supreme Court, Boniface Alexandre, is sworn in as interim president.
- March 2
- March 10 – Five British men are released from detention at Camp Delta, Guantanamo Bay. After they land at RAF Brize Norton, 4 of them are immediately arrested for questioning.
- March 11 – Terrorists execute simultaneous attacks, with bombs in 4 rush-hour trains in Madrid, killing 191 people.
- March 17 – A pogrom-like organized violence breaks out over 2 days in Kosovo; 19 people are killed, 8,000 Serbian homes burned, schools and businesses vandalized, and over 300 Orthodox monasteries and churches burned and destroyed.
- March 25 – British prime minister Tony Blair visits Libyan leader Colonel Muammar Gaddafi, in return for the dismantling of Libya's weapons of mass destruction programme in December 2003 (the first time a major Western leader had visited the nation in several decades).
- March 28 – The first ever reported South Atlantic hurricane makes landfall in southern Brazil in the state of Santa Catarina – the hurricane is dubbed Cyclone Catarina.
- March 29
- April 1 – Google releases Gmail.
- April 8 – Darfur conflict: The Humanitarian Ceasefire Agreement is signed by the Sudanese government and 2 rebel groups.
- April 17 – Israeli helicopters fire missiles at a convoy of vehicles in the Gaza Strip, killing the Gaza leader of Hamas, Abdel Aziz al-Rantisi.
- April 20 – In Iraq, 12 mortars are fired on Abu Ghraib Prison by insurgents; 22 detainees are killed and 92 wounded.
- April 22 – Ryongchon disaster: Two trains carrying explosives and fuel collide in Ryongchon, North Korea, killing 161 people, injuring 1,300 and destroying thousands of homes.
- April 24 – Referendums on the Annan Plan for Cyprus, which proposes to re-unite the island, take place in both the Greek-controlled and the Turkish-controlled parts. Although the Turkish Cypriots vote in favour, the Greek Cypriots reject the proposal.
- May 1 – The largest expansion to date of the European Union takes place, extending the Union by 10 member-states: Poland, Lithuania, Latvia, Estonia, the Czech Republic, Slovakia, Slovenia, Hungary, Malta and Cyprus.
- May 9 – Chechen president Akhmad Kadyrov is killed by a landmine placed under a VIP stage throughout a World War II memorial parade in Grozny.
- May 12 – An American civilian contractor in Iraq, Nick Berg, is shown being decapitated by a group allegedly linked to al-Qaeda on a web-distributed video.
- May 14 – Frederik, Crown Prince of Denmark, marries Australian Mary Donaldson in Copenhagen.
- May 17 – Massachusetts legalises same-sex marriage, in compliance with a ruling from the state's Supreme Judicial Court (Goodridge v. Department of Public Health).
- May 19 – Jeremy Sivits pleads guilty in a court-martial in connexion with alleged abuse of Iraqi prisoners at Abu Ghraib prison in Baghdad.
- May 24 – North Korea bans mobile phones (see Telecommunications in North Korea).
- May 26 – Terry Nichols is convicted by an Oklahoma state court on murder charges stemming from the 1995 Oklahoma City bombing.
- June 8 – The first transit of Venus after 1882 occurs; the following one occurred in 2012.
- June 11 – Terry Nichols is spared the death penalty by an Oklahoma state court on murder charges stemming from the 1995 Oklahoma City bombing.
- June 12 – A 1.3 kg chondrite type meteorite strikes a house in Ellerslie, New Zealand, causing serious damage but no injuries.
- June 21 – In Mojave, California, SpaceShipOne becomes the first privately funded spaceplane to achieve spaceflight.
- June 28 – The U.S.-led coalition occupying Iraq transfers sovereignty to an Iraqi Interim Government.
- June 30 – Preliminary hearings begin in Iraq in the trial of former president Saddam Hussein, for war crimes and crimes against humanity.
- July 1
- July 4
- August 1
- August 3
- August 9 – At the Mihama Nuclear Power Plant, a pipe leaking hot water and steam kills 5 and injures 6 others, in the second worst nuclear disaster in Japan.
- August 13–29 – The 2004 Summer Olympics are held in Athens, Greece.
- August 22 – Armed robbers steal Edvard Munch's The Scream, Madonna, and additional paintings from the Munch Museum in Oslo, Norway.
- August 24 – Two airliners in Russia, carrying a total of 89 passengers, crash within minutes of each additional after flying out of Domodedovo International Airport, leaving no survivors. Authorities suspect suicide attacks by rebels from Chechnya to be the cause of the crashes.
- August 26 – During the Republican National Convention over 1800 individuals were arrested by the authorities in New York City, USA. However ninety percent of those charges were eventually dropped.
- September 1 – Chechen terrorists take 1,128 people hostage, mostly children, in a school in the Beslan school hostage crisis. The hostage-takers demand the release of Chechen rebels imprisoned in neighbouring Ingushetia and the independence of Chechnya from Russia.
- September 2 – The United Nations Security Council adopts Resolution 1559, calling for the removal of all foreign troops from Lebanon. This measure is largely aimed at Syrian troops.
- September 3 – Russian forces end the siege at a school in Beslan, Northern Ossetia; 334 people are killed and at least 700 people injured.
- September 9 – A bomb blast outside the Australian embassy in Jakarta, Indonesia, kills 11 and injures up to 100 people.
- September 17
- September 21 – Construction of the Burj Khalifa begins.
- September 29 – In Mojave, California, the first Ansari X Prize flight takes place of SpaceShipOne, which is competing with a number of spacecraft (including Canada's Da Vinci Project, claimed to be its closest rival) and goes on to win the prize on October 4.
- October 8 – Suicide bombers detonate 2 bombs at the Red Sea resort of Taba, Egypt, killing 34 people, mainly Israeli tourists and Egyptian workers.
- October 14 – Prince Norodom Sihamoni is chosen as the new king of Cambodia.
- October 19 – A team of explorers reaches the bottom of Krubera Cave, world's deepest cave. The depth reached is 2,080 metres (6,824 feet), setting a world record ().
- October 20
- October 21 – The Ministry of Defence approves the deployment of the Black Watch regiment of the British Army to Baghdad, Iraq, after a request for assistance by the U.S. government.
- October 23 – A magnitude 6.7 earthquake and aftershocks of similar scale occur in the Tokamachi area. A landslide occurs on the outskirts of Nagaoka. According to Japanese officials, 68 people are killed, 4,085 are injured, and 103,000 are rendered homeless.
- October 24 – Brazil successfully launches its first rocket into space.
- October 26 – The Cassini probe passes within 1,200 km of Titan.
- October 27 – Details of the discovery of a new, recent species of fossil hominid, Homo floresiensis, from the island of Flores, Indonesia, are published.
- October 29 – European heads of state sign in Rome the Treaty and Final Act, establishing the first European Constitution.
- November 2 – United States presidential election, 2004: Republican incumbent President George W. Bush is declared the winner over his Democratic challenger, U.S. Senator John F. Kerry, in a close election.
- November 6 – In Ivory Coast, National Army bombings kill 9 people, including French U.N. soldiers. French U.N. forces retaliate by destroying the National Army's air force.
- November 7 – U.S. forces launch a major assault on the Iraqi town of Fallujah, in an effort to rid the area of insurgents before the Iraqi elections in January.
- November 13 – After six days of intense battles, the Iraqi town of Fallujah is fully occupied by U.S. forces.
- November 16
- November 22 – The Orange Revolution begins when the government of the Ukraine is accused of electoral fraud against presidential candidate Viktor Yushchenko.
- November 23 – World of Warcraft was released.
- November 28 – A male Poʻouli dies of avian malaria at the Maui Bird Conservation Center in Olinda before it can breed, making the species in all probability extinct.
- December 6 – Terrorists attack the U.S. Consulate in Jeddah, Saudi Arabia, killing several people.
- December 8 – Dimebag Darrell, former guitarist for the heavy metal band Pantera, is murdered on stage by a deranged fan while performing with his new band Damageplan.
- December 10 – New Zealand bans smoking in all public places, including bars.
- December 14 – The world's tallest bridge, the Millau bridge over the River Tarn in the Massif Central mountains, France, is opened by President Jacques Chirac.
- December 15 – Albanian terrorists take a bus and its passengers hostage in Athens, Greece, and demand €1 million in ransom money.
- December 16 – The House of Lords rules that the British Government breaches human rights legislation, by detaining without trial foreign nationals suspected of being terrorists.
- December 21 – Iraqi insurgents attack a U.S. military base in the city of Mosul, killing 22 people.
- December 26 – The 9.1–9.3 Mw Indian Ocean earthquake shakes northern Sumatra with a maximum Mercalli intensity of IX (Violent). One of the largest observed tsunamis follows, affecting coastal areas of Thailand, India, Sri Lanka, the Maldives, Malaysia, Myanmar, Bangladesh, and Indonesia. The death toll across a number of these nations is 230,000–280,000.
- December 27 – Astrophysicists from the Max Planck Institute for Extraterrestrial Physics in Garching near Munich measure the strongest burst from a magnetar. At 21:30:26 UT the earth is hit by a huge wave front of gamma and X-rays. It is the strongest flux of high-energetic gamma radiation measured so far.
- December 30 – A fire in a Buenos Aires night club (República Cromagnon) kills 194 people throughout a rock concert.
- December 31
- January 4 – Joan Aiken, English author (b. 1924)
- January 7 – Ingrid Thulin, Swedish actress (b. 1926)
- January 9 – Norberto Bobbio, Italian philosopher (b. 1909)
- January 13 – Harold Shipman, British serial killer (b. 1946)
- January 14
- January 22 – Ann Miller, American dancer and actress (b. 1923)
- January 25
- January 29 – O. W. Fischer, Austrian actor (b. 1915)
- February 3 – Jason Raize, American actor and singer (b. 1975)
- February 14 – Marco Pantani, Italian cyclist (b. 1970)
- February 17 – José López Portillo, President of Mexico (b. 1920)
- February 21 – John Charles, Welsh footballer (b. 1931)
- February 26
- February 27 – Paul Sweezy, American economist and editor (b. 1910)
- February 28 – Daniel J. Boorstin, American historian and Librarian of Congress (b. 1914)
- March 2 – Mercedes McCambridge, American actress (b. 1916)
- March 4 – Claude Nougaro, French singer (b. 1929)
- March 7 – Paul Winfield, American actor (b. 1939)
- March 8 – Muhammad Zaidan, founder of the Palestine Liberation Front (b. 1948)
- March 15 – John Pople, English chemist, Nobel Prize laureate (b. 1925)
- March 20 – Juliana, Queen regnant of the Netherlands (1948-1980) (b. 1909)
- March 22 – Ahmed Yassin, Palestinian co-founder of Hamas (b. 1937)
- March 26 – Jan Sterling, American actress (b. 1921)
- March 28 – Peter Ustinov, English actor and director (b. 1921)
- April 1 – Carrie Snodgress, American actress (b. 1945)
- April 18 – Kamisese Mara, first Prime Minister of Fiji and President of Fiji (b. 1920)
- April 19 – John Maynard Smith, English biologist (b. 1920)
- April 22 – Pat Tillman, American football player and U.S. Army Ranger (b. 1976)
- April 24 – Estée Lauder, American cosmetics entrepreneur (b. 1906)
- April 26 – Hubert Selby, Jr., American writer (b. 1928)
- May 7 – Nicholas Berg, American businessman (executed by decapitation) (b. 1978)
- May 14 – Anna Lee, British actress (b. 1913)
- May 16 – Marika Rökk, Egyptian-born Austrian singer, dancer and actress (b. 1913)
- May 17
- May 22 – Richard Biggs, American actor (b. 1960)
- June 5 – Ronald Reagan, American politician and actor, 40th President of the United States (b. 1911)
- June 7 – Quorthon, Swedish musician (b. 1966)
- June 10 – Ray Charles, American singer and musician (b. 1930)
- June 11 – Xenophon Zolotas, Greek economist, interim 177th Prime Minister of Greece (b. 1904)
- June 16 – Thanom Kittikachorn, Thai military dictator, 10th Prime Minister of Thailand (b. 1912)
- June 26 – Naomi Shemer, Israeli songwriter (b. 1931)
- July 1 – Marlon Brando, American actor (b. 1924)
- July 5
- July 6 – Thomas Klestil, Austrian politician and diplomat, tenth President of Austria (b. 1932)
- July 13 – Carlos Kleiber, Austrian conductor (b. 1930)
- July 16 – Pat Roach, British wrestler and actor (b. 1937)
- July 19 – Zenkō Suzuki, Japanese politician, 70th Prime Minister of Japan (b. 1911)
- July 21
- July 22 – Sacha Distel, French singer (b. 1933)
- July 28 – Francis Crick, English molecular biologist, recipient of the Nobel Prize in Physiology or Medicine (b. 1916)
- August 1 – Philip Abelson, American physicist, Nobel Prize laureate (b. 1913)
- August 3 – Henri Cartier-Bresson, French photographer (b. 1908)
- August 6 – Rick James, American musician (b. 1948)
- August 8 – Fay Wray, Canadian actress (b. 1907)
- August 9 – David Raksin, American composer (b. 1912)
- August 12 – Godfrey Hounsfield, English electrical engineer and inventor, recipient of the Nobel Prize in Physiology or Medicine (b. 1919)
- August 13 – Julia Child, American chef (b. 1912)
- August 14 – Czesław Miłosz, Polish-born writer, Nobel Prize laureate (b. 1911)
- August 15 – Sune Bergström, Swedish biochemist, recipient of the Nobel Prize in Physiology or Medicine (b. 1916)
- August 17 – Gérard Souzay, French baritone (b. 1918)
- August 18 – Elmer Bernstein, American composer (b. 1922)
- August 24 – Elisabeth Kübler-Ross, Swiss-born psychiatrist (b. 1926)
- August 26 – Laura Branigan, American singer (b. 1952)
- August 30 – Fred Lawrence Whipple, American astronomer (b. 1906)
- September 11 – Patriarch Peter VII of Alexandria (b. 1949)
- September 13 – Luis E. Miramontes, Mexican chemist (b. 1925)
- September 15 – Johnny Ramone, American guitarist (Ramones) (b. 1948)
- September 18 – Russ Meyer, American director and photographer (b. 1922)
- September 20 – Brian Clough, British football manager of Nottingham Forest and Derby County (b. 1935)
- September 22 – Ray Traylor, American professional wrestler (b. 1962)
- September 24 – Françoise Sagan, French writer (b. 1935)
- October 1 – Richard Avedon, American photographer (b. 1923)
- October 3 – Janet Leigh, American actress (b. 1927)
- October 4 – Gordon Cooper, American astronaut (b. 1927)
- October 5
- October 8 – Jacques Derrida, Algerian-born French literary critic (b. 1930)
- October 10 – Christopher Reeve, American actor and activist (b. 1952)
- October 23 – Bill Nicholson, British footballer (b. 1919)
- October 25 – John Peel, British radio disc jockey (b. 1939)
- October 29 – Princess Alice, Duchess of Gloucester (b. 1901)
- November 2
- November 3 – Sergei Zholtok, Latvian hockey player (b. 1972)
- November 7
- November 9
- November 11 – Yasser Arafat, Palestinian leader, recipient of the Nobel Peace Prize (b. 1929)
- November 13 – Ol' Dirty Bastard, American rapper (b. 1968)
- November 19 – John Robert Vane, British pharmacologist, recipient of the Nobel Prize in Physiology or Medicine (b. 1927)
- November 23 – Rafael Eitan, Israeli politician (b. 1929)
- November 29 – John Drew Barrymore, American actor (b. 1932)
- December 1 – Prince Bernhard of Lippe-Biesterfeld, German born Prince Consort of the Netherlands (1948-1980) (b. 1911)
- December 2 – Alicia Markova, English ballerina (b. 1910)
- December 8 – Dimebag Darrell, American guitarist (Pantera and Damageplan) (b. 1966)
- December 14 – Fernando Poe Jr., Filipino actor (b. 1939)
- December 19
- December 23 – P. V. Narasimha Rao, Indian politician, tenth Prime Minister of India (b. 1921)
- December 26 – Reggie White, American football player (b. 1961)
- December 28
- December 30 – Artie Shaw, American musician (b. 1910)
- December 31 – Gérard Debreu, French-born economist, Nobel Prize laureate (b. 1921)
- Physics – David J. Gross, H. David Politzer, Frank Wilczek
- Chemistry – Aaron Ciechanover, Avram Hershko, Irwin Rose
- Physiology or Medicine – Linda B. Buck, Richard Axel
- Literature – Elfriede Jelinek
- Peace – Wangari Maathai
- Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel – Finn E. Kydland, Edward C. Prescott