The following events occurred in August 1903:
- Polish Cardinal Jan Puzyna de Kosielsko issues a veto (jus exclusivae) against the nomination of the front runner, Cardinal Mariano Rampolla, in the name of Emperor Franz Josef I of Austria. The veto is refused, but Rampolla loses some of his support.
- Died: Calamity Jane (Martha Jane Canary), frontierswoman and professional scout, 51 (alcohol-related inflammation of the bowel and/or pneumonia)
- The Ilinden–Preobrazhenie Uprising, organized by the Secret Macedonian-Adrianople Revolutionary Organization, breaks out in the Ottoman provinces of Macedonia and Adrianople.
- Pittencrieff Park in Dunfermline, Scotland, is gifted to the people of the town by Dunfermline native Andrew Carnegie.
- The US schooner Tennie and Laura capsizes and sinks in Lake Michigan, 9 nautical miles (17 km) off Port Washington, Wisconsin. One of the two crew members is killed.
- The final of Sweden's 1903 Svenska Mästerskapet football tournament is won by Göteborgs IF.
- The 2nd Congress of the Russian Social Democratic Labour Party, presided over by Lenin, is forced by police action to relocate from Brussels, Belgium, to London, UK.
- The second tropical cyclone of the season is observed east of the Windward Islands.
- King Edward VII of the United Kingdom appoints Henry Northcote, 1st Baron Northcote, as the next Governor-General of Australia with effect from January 1904.
- During a Philadelphia Phillies home match at Baker Bowl a balcony collapses, killing four people and injuring many more. The Phillies temporarily move to Columbia Park pending repairs.
- The British government writes to other parties involved in the Berlin Conference of 1884-5, with details of abuses and atrocities in the Congo for which King Leopold II of Belgium was deemed responsible.
- At his coronation ceremony, Pope Pius X shocks his entourage by wearing a simple pectoral cross made of gilded metal, which he says is the only one he owns.
- The tropical storm observed on August 6 strikes Martinique, leaving thousands homeless in Fort-de-France and surrounding villages. Eight people are killed.
- Kerry GAA defeat Cork GAA in the semi-final of the All-Ireland Senior Football Championship - Munster division at Millstreet.
- Paris Métro train fire: After several attempts to extinguish a fire on the wooden-bodied Train 43–52, the flames get out of control and 84 people are killed, most at Couronnes station.
- The Oseberg Ship, a 9th-century Viking ship, is discovered in a large burial mound at a farm near Tønsberg, Vestfold, Norway.
- A hurricane strikes Jamaica, devastating the island's northern shore and wrecking several ships. Between 65 and 90 people are killed.
- Two people are killed when an earthquake of magnitude 8.1 strikes Kythera, Greece
- Died: Eugenio María de Hostos, 64, Puerto Rican lawyer, philosopher and campaigner
- Born: James Gould Cozzens, US novelist, in Chicago (died 1978)
- Died: Robert Gascoyne-Cecil, 3rd Marquess of Salisbury, 73, three times Prime Minister of the United Kingdom
- Born: Arthur Godfrey, US broadcaster, in Manhattan (died 1983)
- Straub, Patrick (10 November 2009). It Happened in South Dakota: Remarkable Events That Shaped History. Rowman & Littlefield. p. 33. ISBN 978-0-7627-6171-5.
- "Mr. Carnegie And Dunfermline". The Times (37153). London. 1903-08-07. p. 10.
- Alsiö, Martin; Frantz, Alf; Lindahl, Jimmy; et al., eds. (2004). 100 år: Svenska fotbollförbundets jubileumsbok 1904-2004, del 2: statistiken. Vällingby: Stroemberg Media Group. ISBN 91-86184-59-8.
- Herbermann, Charles, ed. (1913). . Catholic Encyclopedia. New York: Robert Appleton Company.
- "Fourth Generation". ancestry.com. Retrieved 12 May 2016., date given as 18 August Gregorian calendar, which converts to 5 August in the Julian calendar used in Romania at the time.
- Krupskaya, Reminiscences of Lenin
- The Advertiser, 10 August 1903, page 4
- "Grand Stand Falls; 4 Killed, 125 Injured" (PDF). New York Times. August 9, 1903.
- Macht, Norman L.; Connie Mack, III (2007). Connie Mack and the Early Years of Baseball. University of Nebraska Press. p. 316. ISBN 0-8032-3263-2. Retrieved May 22, 2009.
- William Roger Louis (2006). Ends of British Imperialism: The Scramble for Empire, Suez, and Decolonization. I.B.Tauris. pp. 154–. ISBN 978-1-84511-347-6.
- Avella, Steven M; Zalar, Jeffrey (Fall 1997), "Sanctity in the Era of Catholic Action: The Case of St. Pius X", Catholic Historian (Spirituality and Devotionalism ed.), US, 15 (4), pp. 57–80
- "Renders 5,000 Homeless". Pittsburgh Daily Post. Washington, D.C. August 12, 1903. p. 1. Retrieved May 30, 2016 – via Newspapers.com.
- Durham, Keith. Noon, Steve. (2002). Viking Longship Osprey Publishing ISBN 1-84176-349-7
- "Ninety Lives Lost in Jamaica Storm". Los Angeles Herald-Express. Washington, D.C. September 18, 1903. Retrieved May 17, 2016 – via California Digital Newspaper Collection.
- "Centennial Earthquake Catalog". United States Geological Survey. August 11, 1903. Retrieved November 16, 2015.
- "Significant Earthquake GREECE: MITATA (KYTHERA)". National Geophysical Data Center. August 11, 1903. Retrieved November 16, 2015.
- Sánchez, Luis Alberto. "Eugenio María de Hostos". Escritores representativos de América. Madrid: Gredos 2 (1963): 147–54
- Jose F. Partagas (1997). Year 1903 (PDF). Atlantic Oceanographic and Meteorological Laboratory (Report). Miami, Florida: National Oceanic and Atmospheric Administration. pp. 48–52. Retrieved May 17, 2016.
- Miller, David W.: Church, State and Nation in Ireland 1898–1921 Land for the People pp.77–94, Gill & Macmillan (1973) ISBN 0-7171-0645-4
- "Storm's Work in Mexico" (PDF). The New York Times. Austin, Texas. August 22, 1903. Retrieved May 30, 2016.
- Cummings, John (1980). Railway Motor Buses and Bus Services in the British Isles 1902–1933, volume 2. Oxford: Oxford Publishing Company. ISBN 0-86093-050-5.
- "The Pioneers : An Anthology : Karl Jatho (1873–1933)". Retrieved 6 August 2016.
- Ann Savours (4 April 2013). The Voyages of the Discovery: An Illustrated History of Scott's Ship. Seaforth Publishing. pp. 54–. ISBN 978-1-84832-702-3.
- "Tennis Final Postponed" (PDF). The New York Times. August 26, 1903.
- ALRC Report 92: A Review of the Judiciary Act 1903 and Related Legislation – Australian Law Reform Commission Review (July 2001)
- Paul J. Vanderwood (1998). The Power of God Against the Guns of Government: Religious Upheaval in Mexico at the Turn of the Nineteenth Century. Stanford University Press. pp. 384–. ISBN 978-0-8047-3039-6.
- Elizabeth Taylor (31 May 2013). The Old World and the New: The Marriage and Colonial Adventures of Lord and Lady Northcote. Cambridge Scholars Publishing. pp. 74–. ISBN 978-1-4438-4919-7.
- Playbill (October 1903)