Lady Mabel Florence Harriet Wentworth-Fitzwilliam (14 July 1870 – 26 September 1951) was an English socialist politician, later known as Lady Mabel Smith. Her father was William Wentworth Fitzwilliam, Viscount Milton, the eldest son of William Wentworth-FitzWilliam, 6th Earl FitzWilliam. Her father died before inheriting the Earldom and it passed to her brother, William Wentworth-FitzWilliam, 7th Earl FitzWilliam whose lifestyle she criticised; "he had so much and everyone else had so little". In 1918 she visited France as Inspector of Yorkshire's .