John Gordon Swift MacNeill (11 March 1849 – 24 August 1926) was an Irish Protestant Nationalist politician and MP, in the House of Commons of the United Kingdom of Great Britain and Ireland for South Donegal from 1887 until 1918, Professor of Constitutional and Criminal Law at the King's Inns, Dublin, 1882–88, and Professor of the Law of Public and Private Wrongs at the National University of Ireland from 1909.
He was also a well-known author on law and nationalist issues, and became a QC (Queen's Counsel) (later KC) in 1893.