Frances Seymour, Duchess of Somerset (born 1699)

Frances Seymour, Duchess of Somerset (1699 – 1754), née Thynne, was a British noblewoman. She was the second wife of Algernon Seymour, 7th Duke of Somerset.

Frances was the daughter of Henry Thynne and his wife, Grace Strode. Her marriage to Algernon Seymour took place before 1715. Upon her husband's succession to the dukedom of Somerset in 1748, Frances became Duchess of Somerset.

Her husband had previously been married to Frances Finch, and had two surviving daughters by that marriage, Elizabeth Seymour, Duchess of Northumberland, and Lady Frances Seymour. Through her step-daughters' marriages, Frances became connected to powerful families, further cementing her place within the British aristocracy.

The Duchess of Somerset died in 1754. She is remembered primarily as the wife of a prominent Duke and a member of the high society of her time. Details about her personal life and activities are scarce compared to those of her husband and step-daughters.