• February 15 - Morris Michtom and his wife Rose introduce the first teddy bear in America.
• February 23 - Cuba leases Guantanamo Bay to the United States "in perpetuity"
• March 2 - In New York City the Martha Washington Hotel opens, becoming the first hotel exclusively for women.
• March 14 - The Hay-Herran Treaty, granting the United States the right to build the Panama Canal, is ratified by the United States Senate. The Colombian Senate would later reject the treaty.
• March 31 - Possible first powered heavier-than-air flight, Richard Pearse, New Zealand (some date it to 1902)
• May 18 - Opening of Port of Burgas, Bulgaria.
• July 23 - Dr. Ernst Pfenning of Chicago, Illinois becomes the first owner of a Ford Model A.
• April 29 - 30,000,000 cubic metre landslide kills 70 in Frank, Alberta
• August 4 - Pope Pius X elected
• November 3 - With the encouragement of the United States, Panama proclaims itself independent from Colombia. US President Theodore Roosevelt wanted the United States to build the Panama Canal but were blocked by Colombia.
• November 17 - The Russian Social Democratic Labor Party splits into two groups; the Bolsheviks (Russian for "majority") and Mensheviks (Russian for "minority"). (NOTE: Later the Mensheviks became the majority party, meaning that the Mensheviks became the bolsheviks and the Bolsheviks mensheviks).
• November 18 - The Hay-Bunau-Varilla Treaty is signed by the United States and Panama, giving the Americans exclusive rights over the Panama Canal Zone.
• November 23 - Colorado Governor James Peabody sends the state militia into the town of Cripple Creek to break up a miners' strike.
• December 17 - Orville Wright flies aircraft with a petrol engine in first documented successful controlled powered heavier-than-air flight.
• December 30 - A fire at the Iroquois Theater in Chicago kills 600.

• Thomas Hunt Morgan discovers that chromosomes contain genes.

Year in topic

• 1903 in film
  • The Great Train Robbery, by Edwin S. Porter
• 1903 in literature
• 1903 in music
  • February 11 - Anton Bruckner's 9th Symphony premieres in Vienna
• 1903 in sports

Births

• January 11 - Hans Redlich, composer (+1968)
• January 16 - William Grover-Williams Grand Prix motor racing driver/war hero (+1945)
• January 18 - Werner Hinz, actor (+ 1985)
• January 22 - Fritz Houtermans, physicist (+ 1966)
• January 23 - Randolph Scott, actor (+ 1987)
• January 27 - John Carew Eccles, psychologist, winner of Nobel Prize in Physiology or Medicine 1963, (+ 1997)
• February 2 - Bartel Leendert van der Waerden, mathematician (+ 1996)
• February 5 - Eugen Weidmann, murderer (+ 1939)
• February 6 - Claudio Arrau, pianist (+ 1991)
• February 11 - Alan Paton, writer (+ 1988)
• February 11 - Rex Lease, American actor (+1966)
• February 13 - Georges Simenon, thriller writer (+ 1989)
• February 16 - Edgar Bergen, ventriloquist (+ 1978)
• February 21 - Anaïs Nin, writer (+ 1977)
• February 21 - Raymond Queneau, French poet and novelist (+ 1976)
• February 22 - Frank P. Ramsey, mathematician (+ 1930)
• February 22 - Morley Callaghan (+1990)
• February 24 - Franz Burda, German publisher (+ 1986)
• February 27 - Grethe Weiser, actress (+ 1970)
• February 28 - Vincente Minnelli, director (+ 1986)
• March 10 - Bix Beiderbecke, jazz trumpeter (+ 1931)
• March 11 - Lawrence Welk, Champagne musicmaker (+ 1992)
• March 18 - O. E. Plauen, illustrator and cartoonist (+ 1944)
• April 3 - Peter Huchel, lyricist and author of radio plays (+ 1981)
• April 6 - Mickey Cochrane, baseball player (+ 1962)
• April 6 - Doc Edgerton, MIT professor of electrical engineering (+ 1990)
• April 10 - Clare Boothe Luce, publisher, writer (+ 1987)
• April 15 - John Williams, actor (+ 1983)
• April 25 - Andrey Nikolaevich Kolmogorov, Russian mathematician (+ 1987)
• May 2 - Benjamin Spock, pediatrician (+ 1998)
• May 3 - Bing Crosby, singer (+ 1977)
• May 8 - Fernandel, actor (+ 1971)
• May 20 - Barbara Hepworth, sculptor (+ 1975)
• May 21 - Frank Sargeson, writer (+1982)
• May 29 - Bob Hope, comedian (+ 2003)
• June 6 - Aram Khachaturian, composer (+ 1978)
• June 8 - Marguerite Yourcenar, writer (+ 1987)
• June 12 - Emmett Hardy, jazz musician (+ 1925)
• June 19 - Lou Gehrig, baseball player (+ 1941)
• June 21 - Al Hirschfeld, caricaturist (+ 2003)
• June 25 - George Orwell, author (+ 1950)
• June 25 - Pierre Brossolette, journalist, French Resistance (+ 1944)
• July 1 - Amy Johnson, aviator (+ 1941)
• July 2 - Olav V, King of Norway (+ 1991)
• July 2 - Alec Douglas-Home, British prime minister (+ 1995)
• July 10 - John Wyndham, Author (+ 1969)
• July 13 - Kenneth Clark (+ 1983)
• July 21 - Roy Neuberger, financier and art collector
• August 7 - Louis Leakey, British archaeologist (+ 1972)
• September 7 - Shimaki Kensaku, Japanese author (+ 1945)
• September 9 - Phyllis Whitney, mystery writer
• September 11 - Theodor Adorno (+ 1969)
• September 13 - Claudette Colbert (+ 1996)
• September 21 - Preston Tucker, designer of the Tucker automobile (+ 1956)
• September 25 - Mark Rothko, painter (+ 1970)
• October 4 - John Vincent Atanasoff (+ 1995)
• October 1 - Vladimir Horowitz, pianist (+ 1989)
• October 28 - Evelyn Waugh, comic, satirical and tragic novelist (+ 1966)
• November 2 - Edgard Potier, Belgian SOE agent, WW II hero (+ 1944)
• November 3 - Walker Evans, (+ 1975)
• November 6 - Carl Rakosi, Objectivist poet
• November 7 - Konrad Lorenz, zoologist (+ 1989)
• November 19 - Nancy Carroll, actress (+ 1965)
• November 27 - Lars Onsager, 1968 Nobel Prize in Chemistry (+ 1976)
• December 5 - Johannes Heesters, singer, actor, entertainer
• December 12 - Alfred Leslie Rowse, historian (+ 1997)
• December 12 - Yasujiro Ozu, Japanese film director (+ 1963)
• December 24 - Joseph Cornell, sculptor (+ 1972)
• December 28 - John von Neumann, Hungarian-American mathematician (+ 1957)

Deaths

• January 28 - Robert Planquette, French musical composer (* 1850)
• January 30 - Giustina Pecori-Suárez, third wife of Jerome Bonaparte (* 1811)
• February 7 - James Glaisher, meteorologist and aeronaut (* 1809)
• February 11 - Henryk Szulc, composer (* 1836)
• February 22 - Hugo Wolf, composer (* 1860)
• February 26 - Richard Jordan Gatling, inventor (* 1818)
• March 6 - Bruno Paulin Gaston Paris, French scholar (* 1839)
• March 13 - George Granville Bradley (* 1821)
• March 16 - Judge Roy Bean, Old West pioneer
• March 28 - Emile Baudot, telegraph engineer (* 1845)
• April 19 - Oliver Mowat, Premier of Ontario (* 1820)
• April 28 - Willard Gibbs, physical chemist (* 1839)
• May 9 - Paul Gauguin, Impressionist painter (* 1848)
• June 19 - Herbert Vaughan, cardinal and Archbishop of Westminster (* 1832)
• July 11 - William Ernest Henley, poet, critic, and editor (* 1849)
• July 17 - James McNeill Whistler, painter (* 1834)
• July 20 - Pope Leo XIII (* 1810)
• September 18 - Alexander Bain, Scottish philosopher (* 1818)
• November 1 - Theodor Mommsen, German classical scholar/historian (* 1817)
• November 12 - Camille Pissarro, painter (* 1830)
• December 8 - Herbert Spencer, English philosopher (* 1820)

Nobel Prizes

• Physics - Antoine Henri Becquerel, Pierre Curie, Marie Curie
• Chemistry - Svante August Arrhenius
• Medicine - Niels Ryberg Finsen
• Literature - Bjørnstjerne Bjørnson
• Peace - William Randal Cremer\n