Harman Blennerhassett (8 October 1765 – 2 February 1831) was an Anglo-Irish lawyer, a member of the Society of United Irishmen who emigrated in advance of their rebellion in 1798 to become a socially and politically distinguished plantation owner in western Virginia. Implicated in the Burr conspiracy, an alleged military plot with Britain to separate Louisiana territory from the American union, he was twice arrested and financially ruined. His last years were spent in England.