Louisa Thynne, Viscountess Weymouth

Louisa Thynne, Viscountess Weymouth (née Carteret), was born on 15 September 1714 and died on 25 December 1736. She was an English noblewoman, the daughter of John Carteret, 2nd Earl Granville, and his first wife, Frances Worsley.

Louisa married Thomas Thynne, 2nd Viscount Weymouth, on 3 July 1733. The marriage occurred four years after the death of Thynne's first wife. Together, they had two children: Thomas Thynne, who became the 1st Marquess of Bath and the 3rd Viscount Weymouth, born on 13 September 1734 and died on 19 November 1796; and Henry Frederick Carteret, born on 17 November 1735 and died on 17 June 1826, who was created the 1st Baron Carteret of Hawnes.

A portrait of Louisa was painted by John Vanderbank, depicting her in "a fancy dress of pink and black."

A legend exists suggesting that her family home, Longleat House, is haunted by her ghost, supposedly mourning her lover who was killed by her husband. However, there is no historical evidence supporting the existence of this lover.

Her friend, Mrs. Delany, recorded her impressions in her memoirs, stating: "I know some who had higher virtues than she had, but none with fewer faults. Her husband's ... loss is irreparable."

Louisa Thynne died in childbirth at her residence in Grosvenor Square, London. She was interred in the family burial site at Longbridge Deverill, Wiltshire. Following her brother Robert Carteret, 3rd Earl Granville's death in 1776, her son succeeded to the Carteret estates.