Viscount Molesworth, of Swords in the County of Dublin, is a title in the Peerage of Ireland.
He was made Lord Molesworth, Baron of Philipstown, of King's County, at the same time, also in the Peerage of Ireland.
His elder son, the second Viscount, notably served as Ambassador to the Kingdom of Sardinia, the Grand Duchy of Tuscany and the Republic of Venice.
On his death, this line of the family also failed and the titles were inherited by his second cousin, the seventh Viscount.
Sophie, Duchess of Edinburgh, is a descendant of the 1st Viscount through her grandmother, Margaret Rhys-Jones (née Molesworth; 1904–1985), who was the great-granddaughter of the Rev.