John Cassidy may refer to:
Arts and entertainment John Cassidy (artist) (1860–1939), Irish sculptor and painter Jack Cassidy (John Joseph Edward Cassidy, 1927–1976), American actor John Cassidy (magician) (born 1967), American magician and balloon artist John Cassidy (children's writer), American children's writer
Law and politics John Edward Cassidy (1896–1984), American lawyer in Illinois John P. Cassidy (1912–?), American politician in Los Angeles John E. Cassidy Jr. (1924–2003), American politician in Illinois
Sports John Cassidy (baseball) (1855–1891), American baseball player John Cassidy (basketball) (born 1947), Canadian basketball player John Cassidy (speed skater) (born 1952), Canadian speed skater John Joe Cassidy (died 1995), Gaelic football player for Cavan
Others John Cassidy (seismologist) (born 1959), Canadian seismologist John Cassidy (journalist) (born 1963), British-American business journalist John Cassidy (chancellor), Australian university chancellor John F. Cassidy, American businessman
See also John Cassaday (1971–2024), American comic book artist John H. Cassady (1896–1969), American naval officer