John or Johnny Byrne may refer to:
- John Byrne (Scottish footballer) (born 1939), Scottish footballer
- Johnny Byrne (footballer) (1939–1999), England international footballer, soccer coach in South Africa
- John Byrne (footballer, born 1949), English footballer for Tranmere Rovers
- John Byrne (footballer, born 1961), English-born footballer for QPR, Sunderland and the Republic of Ireland
- John Byrne (footballer, born 1962), Irish footballer
- John Byrne (VC) (1832–1879), Irish recipient of the Victoria Cross
- John Edgar Byrne (1842–1906), Australian journalist and newspaper proprietor
- John Francis Byrne, creator of the Chaocipher
- Jock Byrne (John Thomas Byrne, 1903–1969), Scottish trade unionist and anti-communist
- John Byrne (businessman) (1919–2013), Irish property developer
- John V. Byrne (born 1928), American marine geologist and academic
- John J. Byrne (1931–2013), American insurance industry executive
- John Byrne (computer scientist) (1933–2016), Irish computer scienctist
- John Byrne (judge) (born 1948), Senior Judge Administrator of the Supreme Court of Queensland
- John K. Byrne (born 1981), founder of the Raw Story news website
- John H. Byrne, American neuroscientist