She was born in Devonshire House as the second daughter of William Cavendish, 5th Duke of Devonshire, by his first wife, the political hostess Lady Georgiana Spencer.
Despite her parents' turbulent marriage, Harriet had a happy childhood.
Harriet's maternal aunt Henrietta arranged for her niece to marry her lover of seventeen years, Granville Leveson-Gower, 1st Earl Granville.
The couple's marriage proved to be happy, and it produced five children.
Granville served as his country's ambassador to France intermittently from 1824 to 1841, and he was awarded an earldom in 1833.
With her position, Harriet acted as hostess to Parisian society, writing detailed accounts that were later published.
She died in 1862 of a stroke, having been widowed fifteen years.