thumb|200px|Sir John Clotworthy (from 1660 1st Viscount Massereene), [[National Portrait Gallery, London. In the top left corner is a depiction of the Round Tower of Windsor Castle with the dates 1648, 1649, 1650, 1651, marked. He was confined here until 1651 with five other distinguished prisoners, when all were dispersed as a precautionary measure]]
thumb|200px|Arms of Clotworthy: Azure, a chevron ermine between three chaplets or
John Clotworthy, 1st Viscount Massereene (died September 1665) was a prominent Anglo-Irish politician.
Origins
He was the son and heir of Sir Hugh Clotworthy (died 1630), High Sheriff of Antrim (who first came to Ireland as a soldier in the Nine Years' War), by his wife Mary Langford, daughter of Roger Langford of West Downe in the parish of Broadwoodwidger in Devon.
A sculpted escutcheon showing the arms of Clotworthy impaling Langford of Kilmackedret was displayed on the facade of Antrim Castle, now demolished. Sir Hugh Clotworthy was the second son of Thomas Clotworthy (born 1530) of Clotworthy in the parish of Wembworthy in Devon, by his third wife Dorothy Parker, a daughter of John Parker (ancestor of the Earl of Morley (1815)) of North Molton in Devon. Sir Hugh's paternal grandmother was Ivota Rashleigh, heiress of Rashleigh in Wembworthy, Devon, to which seat at some time before 1640, the senior line of the Clotworthy family eventually moved their residence from the nearby ancestral seat of Clotworthy.
Career
John was elected to the Irish House of Commons as member for County Antrim in 1634, and was a member of the Long Parliament in England, in 1640, representing Maldon. Clotworthy was a vehement opponent of Thomas Wentworth, 1st Earl of Strafford, in whose impeachment he took an active share. He also took part in the prosecution of Archbishop Laud. He seems to have felt a deep personal hatred for both Strafford and Laud, springing perhaps from profound religious differences. He was criticised for his conduct at Laud's execution, where he thrust himself forward and harangued that elderly man, who was trying to prepare himself for death, on his alleged religious errors.
In 1646, during the Irish Confederate Wars he unsuccessfully negotiated with the Royalist commander James Butler, 1st Duke of Ormonde for the surrender of Dublin to the Parliamentary forces. In 1647, during the English Civil War he was accused of having betrayed the Parliamentarian cause, and also of embezzlement, in consequence of which charges he fled to the Continent, but returned to parliament in June 1648. Wedgwood does however concede that, unlike others who conspired to bring Strafford down, Clotworthy was motivated less by self-interest than by genuine religious fanaticism. Laud's biographer Hugh Trevor-Roper also criticises him for his unpleasant behaviour at Laud's execution, where he engaged him in religious controversy while Laud was trying to prepare himself for death.
Clotworthys today
Many Clotworthys since then have emigrated to other countries around the world, many to America. There are very few known to survive in Northern Ireland.