Viscount Hewett was a title in the Peerage of Ireland. It was created on 9 April 1689 for Sir George Hewett, 2nd Baronet. He was made Baron of Jamestown at the same time, also in the Peerage of Ireland. The Hewett Baronetcy, of Pishiobury in the County of Hertford, was created in the Baronetage of England on 19 July 1660 for Thomas Hewett, Member of Parliament for Windsor. Both titles became extinct on the first Viscount's death in 1689.
The Hewet baronets of Headley Hall were members of another branch of this family.