Blennerhassett, Sir John (d. 1624), judge, born in Norfolk, England, was probably a son of Edward Blennerhassett and Susan Blennerhassett (née Pickerell) of The Laythes, Norwich, and probably also a nephew of Thomas Blenerhasset (qv) (d. 1624). His father (knighted 1603) was granted 1,500 acres in Co. Fermanagh, and other family members were prominent in the plantation of Ulster and in Kerry; the family name is also spelled Blenerhassett. John Blennerhassett was a barrister in Furnival's Inn in 1583; he entered Lincoln's Inn and was called to the bar in 1591. He was a bencher of Lincoln's Inn in 1609, and the same year was knighted and sent to Ireland as an extra baron of the exchequer. He was elected to represent the newly created borough of Belfast in the parliament of 1613, but sat for only one session, because King James decided that the borough had not been granted its charter before the issue of the writs of summons of parliament. He was a commissioner for the Wexford plantation in 1615, was nominated as commissioner of wards in August 1613 and again in April 1615; was a justice of assize courts on the north-east circuit, and was made chief baron of the exchequer in 1620. He died 14 November 1624 and was buried in St Patrick's cathedral, Dublin. He married Ursula Duke (d. 1638) of Suffolk; they had three sons and three daughters. One son was drowned in the River Amazon.
Ball, Judges, i, 242–3, 323; T. W. Moody, ‘The Irish parliament under Elizabeth and James I: a general survey’, RIA Proc., xlv C (1939), 79, 81; Hughes, Patentee officers (1960), 12; Burke, IFR (1976), 134