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John O'Sullivan (columnist) (born 1942), British conservative columnist and editor •
John O'Sullivan (engineer), Australian astronomer and electrical engineer, and one of the inventors of Wi-Fi • Sir
John O'Sullivan (soldier) (1700–1760), Irish soldier, Quartermaster general to Prince Charles Edward Stewart during the Jacobite Rising of 1745 •
John Francis O'Sullivan (1850–1907), Irish-American awarded the Medal of Honor during the Indian Wars •
John L. O'Sullivan (1813–1895), journalist who popularized the phrase "Manifest Destiny" == See also ==