John O'Reilly or Jack O'Reilly may refer to:
Politics John O'Reilly (politician) (born 1951), Canadian politician John B. O'Reilly Jr. (1948–2025), mayor of Dearborn, Michigan John Francis O'Reilly (1888–1942), Australian politician John Joe O'Reilly (politician) (1881–1967), Irish politician John Joseph O'Reilly (1888–1933), Australian politician
Sports John O'Reilly (baseball) (born 1995), American baseball player John O'Reilly (cricketer) (born 1930), Australian cricketer John Joe O'Reilly (Gaelic footballer) (1919–1952)
Other fields John O'Reilly (soldier) (born 1908), Irish soldier John O'Reilly (composer) (born 1940), composer and music theorist John Boyle O'Reilly (1844–1890), poet and novelist John O'Reilly (engineer) (born 1946), vice-chancellor of Cranfield University
See also John O'Reily (1846–1915), Australian bishop John O'Riley (c. 1817–1850), Irish soldier John Reilly (disambiguation) Jack O'Reilly (disambiguation)