James O'Reilly, QC (September 16, 1823 – May 15, 1875) was a Canadian lawyer and politician who represented Renfrew South in the House of Commons of Canada from 1872 to 1874.
He was born in Westport, County Mayo, Ireland, the son of Peter O'Reilly, and came to Upper Canada in 1832 with his father.
O'Reilly studied law with C. O. Benson in Belleville and later with John Willoughby Crawford.
O'Reilly prosecuted Patrick James Whelan who was convicted for the assassination of D'Arcy McGee and hanged.
O'Reilly commanded a company of volunteer militia, reaching the rank of major.