The Treason Act 1800 (39 & 40 Geo.3 c.93) was an Act of the Parliament of the Kingdom of Great Britain. It assimilated the procedure on trials for treason and misprision of treason to the procedure on trials for murder in certain cases. It was passed as a result of an attempt on the life of George III by James Hadfield earlier that year. The Criminal Lunatics Act 1800 was passed at the same time. It further provided that nothing contained in the Act was to be construed to affect the penalty for treason fixed by law.