John Blennerhassett (1930 – 22 September 2013) was an Irish Fine Gael politician from County Kerry.
A farm owner and former drapery buyer, he stood unsuccessfully as a Fine Gael candidate for Dáil Éireann in the Kerry North constituency at the 1969, 1973, and 1977 general elections.
Blennerhassett did not stand for the Dáil again, but after his 1973 defeat he was nominated by the Taoiseach Liam Cosgrave to the 13th Seanad. He was re-elected in 1977 to the 14th Seanad and in 1981 to the 15th Seanad, but the party did not nominate him for the 1982 Seanad election. He blamed the Fine Gael leader Garret FitzGerald, and resigned from the party.
A previous John Blennerhassett was Chief Baron of the Irish Exchequer from 1621–24. He belonged to the Fermanagh branch of the family and was a cousin of Robert Blennerhassett who founded the Kerry branch.
He died in September 2013.